CVE-2026-25639: Axios Denial of Service Vulnerability

Q: What is CVE-2026-25639?

CVE-2026-25639 is a security vulnerability in Axios involving Axios is Vulnerable to Denial of Service via __proto__ Key in mergeConfig under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').

Q: Which Axios versions are affected?

Affected versions include releases prior to 1.13.5, 0.30.3 across affected packages: axios.

Q: What version fixes CVE-2026-25639?

Upgrading to 1.13.5, 0.30.3 (or the latest patched release for your respective branch) resolves the vulnerability.

Q: Is axios affected?

Yes, axios is affected in releases prior to 1.13.5, 0.30.3. Upgrade your dependency to 1.13.5, 0.30.3 or later.

Q: What is the CVSS score of CVE-2026-25639?

CVE-2026-25639 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Q: What CWE is associated with CVE-2026-25639?

CVE-2026-25639 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.).

Q: How can I check npm dependencies for CVE-2026-25639?

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.

HIGH

Advisory Identifier: GHSA-43fc-jf86-j433

CVSS 7.5

CWE-1321 CWE-754

Published 2026-02-09

Advisory Summary

CVE-2026-25639 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Axios libraries in the npm ecosystem. The issue involves axios is vulnerable to denial of service via __proto__ key in mergeconfig. Remediation is available by upgrading affected packages to version 1.13.5, 0.30.3.

CVE-2026-25639 at a Glance

CVE Identifier CVE-2026-25639

GHSA Identifier GHSA-43fc-jf86-j433

Severity HIGH

CVSS v3.1 Base Score 7.5

CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Affected Product Axios

Package Ecosystem npm

Published Date 2026-02-09

Last Updated 2026-05-08

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)

Attack Complexity Low (AC:L)

Privileges Required None (PR:N)

User Interaction None (UI:N)

Scope Unchanged (S:U)

Confidentiality None (C:N)

Integrity None (I:N)

Availability High (A:H)

How to Fix CVE-2026-25639

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: 1.13.5

npm install axios@1.13.5

axios fixed: 0.30.3

npm install axios@0.30.3

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 axios

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-25639, inspect your project dependencies using npm:

npm ls axios

Analyze 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 1.13.5), 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

# Denial of Service via **proto** Key in mergeConfig ### Summary The `mergeConfig` function in axios crashes with a TypeError when processing configuration objects containing `__proto__` as an own property. An attacker can trigger this by providing a malicious configuration object created via `JSON.parse()`, causing complete denial of service. ### Details The vulnerability exists in `lib/core/mergeConfig.js` at lines 98-101: ```javascript utils.forEach(Object.keys({ ...config1, ...config2 }), function computeConfigValue(prop) { const merge = mergeMap[prop] || mergeDeepProperties; const configValue = merge(config1[prop], config2[prop], prop); (utils.isUndefined(configValue) && merge !== mergeDirectKeys) || (config[prop] = configValue); }); ``` When `prop` is `'__proto__'`: 1. `JSON.parse('{"__proto__": {...}}')` creates an object with `__proto__` as an own enumerable property 2. `Object.keys()` includes `'__proto__'` in the iteration 3. `mergeMap['__proto__']` performs prototype chain lookup, returning `Object.prototype` (truthy object) 4. The expression `mergeMap[prop] || mergeDeepProperties` evaluates to `Object.prototype` 5. `Object.prototype(...)` throws `TypeError: merge is not a function` The `mergeConfig` function is called by: - `Axios._request()` at `lib/core/Axios.js:75` - `Axios.getUri()` at `lib/core/Axios.js:201` - All HTTP method shortcuts (`get`, `post`, etc.) at `lib/core/Axios.js:211,224` ### PoC ```javascript import axios from "axios"; const maliciousConfig = JSON.parse('{"__proto__": {"x": 1}}'); await axios.get("https://httpbin.org/get", maliciousConfig); ``` **Reproduction steps:** 1. Clone axios repository or `npm install axios` 2. Create file `poc.mjs` with the code above 3. Run: `node poc.mjs` 4. Observe the TypeError crash **Verified output (axios 1.13.4):** ``` TypeError: merge is not a function at computeConfigValue (lib/core/mergeConfig.js:100:25) at Object.forEach (lib/utils.js:280:10) at mergeConfig (lib/core/mergeConfig.js:98:9) ``` **Control tests performed:** | Test | Config | Result | |------|--------|--------| | Normal config | `{"timeout": 5000}` | SUCCESS | | Malicious config | `JSON.parse('{"__proto__": {"x": 1}}')` | **CRASH** | | Nested object | `{"headers": {"X-Test": "value"}}` | SUCCESS | **Attack scenario:** An application that accepts user input, parses it with `JSON.parse()`, and passes it to axios configuration will crash when receiving the payload `{"__proto__": {"x": 1}}`. ### Impact **Denial of Service** - Any application using axios that processes user-controlled JSON and passes it to axios configuration methods is vulnerable. The application will crash when processing the malicious payload. Affected environments: - Node.js servers using axios for HTTP requests - Any backend that passes parsed JSON to axios configuration This is NOT prototype pollution - the application crashes before any assignment occurs.

CVE-2026-25639 Affected Axios Versions

2 component(s)

Fixed Versions:

1.13.50.30.3

Product / Package	Ecosystem	Affected Versions	Fixed Version
axios npm/axios	npm	≥ 1.0.0 < 1.13.5	1.13.5
axios npm/axios	npm	< 0.30.3	0.30.3

References

GitHub Advisory / Wiki ADVISORY

https://github.com/axios/axios/security/advisories/GHSA-43fc-jf86-j433

NVD — CVE-2026-25639 NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-25639

Axios Source Repository REPOSITORY

https://github.com/axios/axios/pull/7369

Axios Source Repository REPOSITORY

https://github.com/axios/axios/pull/7388

Security Fix Commit FIX COMMIT

https://github.com/axios/axios/commit/28c721588c7a77e7503d0a434e016f852c597b57

Security Fix Commit FIX COMMIT

https://github.com/axios/axios/commit/d7ff1409c68168d3057fc3891f911b2b92616f9e

Axios Source Repository REPOSITORY

https://github.com/axios/axios

Axios Release RELEASE

https://github.com/axios/axios/releases/tag/v0.30.3

Axios Release RELEASE

https://github.com/axios/axios/releases/tag/v1.13.5

Frequently Asked Questions

What is CVE-2026-25639?

CVE-2026-25639 is a security vulnerability in Axios involving Axios is Vulnerable to Denial of Service via __proto__ Key in mergeConfig under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').

Which Axios versions are affected?

Affected versions include releases prior to 1.13.5, 0.30.3 across affected packages: axios.

What version fixes CVE-2026-25639?

Upgrading to 1.13.5, 0.30.3 (or the latest patched release for your respective branch) resolves the vulnerability.

Is axios affected?

Yes, axios is affected in releases prior to 1.13.5, 0.30.3. Upgrade your dependency to 1.13.5, 0.30.3 or later.

What is the CVSS score of CVE-2026-25639?

CVE-2026-25639 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

What CWE is associated with CVE-2026-25639?

CVE-2026-25639 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-2026-25639?

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

View Raw JSON

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-43fc-jf86-j433",
  "modified" : "2026-05-08T13:46:54Z",
  "published" : "2026-02-09T17:46:14Z",
  "aliases" : [ "CVE-2026-25639" ],
  "summary" : "Axios is Vulnerable to Denial of Service via __proto__ Key in mergeConfig",
  "details" : "# Denial of Service via **proto** Key in mergeConfig\n\n### Summary\n\nThe `mergeConfig` function in axios crashes with a TypeError when processing configuration objects containing `__proto__` as an own property. An attacker can trigger this by providing a malicious configuration object created via `JSON.parse()`, causing complete denial of service.\n\n### Details\n\nThe vulnerability exists in `lib/core/mergeConfig.js` at lines 98-101:\n\n```javascript\nutils.forEach(Object.keys({ ...config1, ...config2 }), function computeConfigValue(prop) {\n  const merge = mergeMap[prop] || mergeDeepProperties;\n  const configValue = merge(config1[prop], config2[prop], prop);\n  (utils.isUndefined(configValue) && merge !== mergeDirectKeys) || (config[prop] = configValue);\n});\n```\n\nWhen `prop` is `'__proto__'`:\n\n1. `JSON.parse('{\"__proto__\": {...}}')` creates an object with `__proto__` as an own enumerable property\n2. `Object.keys()` includes `'__proto__'` in the iteration\n3. `mergeMap['__proto__']` performs prototype chain lookup, returning `Object.prototype` (truthy object)\n4. The expression `mergeMap[prop] || mergeDeepProperties` evaluates to `Object.prototype`\n5. `Object.prototype(...)` throws `TypeError: merge is not a function`\n\nThe `mergeConfig` function is called by:\n\n- `Axios._request()` at `lib/core/Axios.js:75`\n- `Axios.getUri()` at `lib/core/Axios.js:201`\n- All HTTP method shortcuts (`get`, `post`, etc.) at `lib/core/Axios.js:211,224`\n\n### PoC\n\n```javascript\nimport axios from \"axios\";\n\nconst maliciousConfig = JSON.parse('{\"__proto__\": {\"x\": 1}}');\nawait axios.get(\"https://httpbin.org/get\", maliciousConfig);\n```\n\n**Reproduction steps:**\n\n1. Clone axios repository or `npm install axios`\n2. Create file `poc.mjs` with the code above\n3. Run: `node poc.mjs`\n4. Observe the TypeError crash\n\n**Verified output (axios 1.13.4):**\n\n```\nTypeError: merge is not a function\n    at computeConfigValue (lib/core/mergeConfig.js:100:25)\n    at Object.forEach (lib/utils.js:280:10)\n    at mergeConfig (lib/core/mergeConfig.js:98:9)\n```\n\n**Control tests performed:**\n| Test | Config | Result |\n|------|--------|--------|\n| Normal config | `{\"timeout\": 5000}` | SUCCESS |\n| Malicious config | `JSON.parse('{\"__proto__\": {\"x\": 1}}')` | **CRASH** |\n| Nested object | `{\"headers\": {\"X-Test\": \"value\"}}` | SUCCESS |\n\n**Attack scenario:**\nAn application that accepts user input, parses it with `JSON.parse()`, and passes it to axios configuration will crash when receiving the payload `{\"__proto__\": {\"x\": 1}}`.\n\n### Impact\n\n**Denial of Service** - Any application using axios that processes user-controlled JSON and passes it to axios configuration methods is vulnerable. The application will crash when processing the malicious payload.\n\nAffected environments:\n\n- Node.js servers using axios for HTTP requests\n- Any backend that passes parsed JSON to axios configuration\n\nThis is NOT prototype pollution - the application crashes before any assignment occurs.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "axios"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.0.0"
      }, {
        "fixed" : "1.13.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.13.4"
    }
  }, {
    "package" : {
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      "name" : "axios"
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    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.30.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.30.2"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/security/advisories/GHSA-43fc-jf86-j433"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-25639"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/pull/7369"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/pull/7388"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/commit/28c721588c7a77e7503d0a434e016f852c597b57"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/commit/d7ff1409c68168d3057fc3891f911b2b92616f9e"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/axios/axios"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/releases/tag/v0.30.3"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/releases/tag/v1.13.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321", "CWE-754" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-09T17:46:14Z",
    "nvd_published_at" : "2026-02-09T21:15:49Z"
  }
}

CVSS V3

7.5 HIGH

Attack Vector Network (AV:N)

Attack Complexity Low (AC:L)

Privileges Required None (PR:N)

User Interaction None (UI:N)

Scope Unchanged (S:U)

Confidentiality None (C:N)

Integrity None (I:N)

Availability High (A:H)

Vector String

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Advisory Metadata

Source ID: GHSA-43fc-jf86-j433
Schema Version: 1.4.0
Published: 2026-02-09 17:46
Last Modified: 2026-05-08 13:46
Database Record File: advisories/github-reviewed/2026/02/GHSA-43fc-jf86-j433/GHSA-43fc-jf86-j433.json