CVE-2026-42039: Axios Denial of Service Vulnerability

Q: What is CVE-2026-42039?

CVE-2026-42039 is a security vulnerability in Axios involving unbounded recursion in toFormData causes DoS via deeply nested request data under CWE-674: Uncontrolled Recursion.

Q: Which Axios versions are affected?

Affected versions include releases prior to 1.15.1, 0.31.1 across affected packages: axios.

Q: What version fixes CVE-2026-42039?

Upgrading to 1.15.1, 0.31.1 (or the latest patched release for your respective branch) resolves the vulnerability.

Q: Is axios affected?

Yes, axios is affected in releases prior to 1.15.1, 0.31.1. Upgrade your dependency to 1.15.1, 0.31.1 or later.

Q: What is the CVSS score of CVE-2026-42039?

CVE-2026-42039 has a CVSS v3.1 base score of 7.5 (MODERATE) 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-2026-42039?

CVE-2026-42039 is classified under CWE-674: Uncontrolled Recursion (The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.).

Q: How can I check npm dependencies for CVE-2026-42039?

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.

MODERATE

Advisory Identifier: GHSA-62hf-57xw-28j9

CVSS 7.5

CWE-674

Published 2026-05-05

Advisory Summary

CVE-2026-42039 is a MODERATE (CVSS 7.5) denial of service vulnerability (CWE-674: Uncontrolled Recursion) affecting Axios libraries in the npm ecosystem. The issue involves unbounded recursion in toformdata causes dos via deeply nested request data. Remediation is available by upgrading affected packages to version 1.15.1, 0.31.1.

CVE-2026-42039 at a Glance

CVE Identifier CVE-2026-42039

GHSA Identifier GHSA-62hf-57xw-28j9

Severity MODERATE

CVSS v3.1 Base Score 7.5

CWE Classification CWE-674: Uncontrolled Recursion

Affected Product Axios

Package Ecosystem npm

Published Date 2026-05-05

Last Updated 2026-06-08

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-2026-42039

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: 1.15.1

npm install axios@1.15.1

axios fixed: 0.31.1

npm install axios@0.31.1

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-2026-42039, 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 1.15.1), 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-674: Uncontrolled Recursion, where the product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack. 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 toFormData recursively walks nested objects with no depth limit, so a deeply nested value passed as request data crashes the Node.js process with a RangeError. ### Details lib/helpers/toFormData.js:210 defines an inner `build(value, path)` that recurses into every object/array child (line 225: `build(el, path ? path.concat(key) : [key])`). The only safeguard is a `stack` array used to detect circular references; there is no maximum depth and no try/catch around the recursion. Because `build` calls itself once per nesting level, a payload nested roughly 2000+ levels deep exhausts V8's call stack. `toFormData` is the serializer behind `FormData` request bodies and `AxiosURLSearchParams` (used by `buildURL` when `params` is an object with `URLSearchParams` unavailable, see `lib/helpers/buildURL.js:53` and `lib/helpers/AxiosURLSearchParams.js:36`). Any server-side code that forwards a client-supplied object into `axios({ data, params })` therefore reaches the recursive walker with attacker-controlled depth. The RangeError is thrown synchronously from inside `forEach`, escapes `toFormData`, and propagates out of the axios request call. In typical Express/Fastify request handlers this terminates the running request; in synchronous startup paths or worker threads it can crash the whole process. ### PoC ```js import toFormData from 'axios/lib/helpers/toFormData.js'; import FormData from 'form-data'; function nest(depth) { let o = { leaf: 1 }; for (let i = 0; i < depth; i++) o = { a: o }; return o; } try { toFormData(nest(2500), new FormData()); } catch (e) { console.log(e.name + ': ' + e.message); } // RangeError: Maximum call stack size exceeded ``` Server-side reachability example: ```js // vulnerable proxy pattern app.post('/forward', async (req, res) => { await axios.post('https://upstream/api', req.body); // req.body user-controlled res.send('ok'); }); // attacker POST /forward with {"a":{"a":{"a":... 2500 deep ...}}} // -> toFormData build() overflows -> request handler crashes ``` Verified on axios 1.15.0 (latest, 2026-04-10), Node.js 20, 3/3 PoC runs reproduce the RangeError at depth 2500. ### Impact A remote, unauthenticated attacker who can influence an object passed to axios as request `data` or `params` triggers an uncaught RangeError inside the synchronous recursive walker. In server-side applications that proxy or re-send client JSON through axios this crashes the request handler and, in worker/cluster setups, the process. Fix by bounding recursion depth in `toFormData`'s `build` function (reject or throw on depths beyond a configurable limit, e.g. 100) or rewriting the walker iteratively.

CVE-2026-42039 Affected Axios Versions

2 component(s)

Fixed Versions:

1.15.10.31.1

Product / Package	Ecosystem	Affected Versions	Fixed Version
axios npm/axios	npm	≥ 1.0.0 < 1.15.1	1.15.1
axios npm/axios	npm	< 0.31.1	0.31.1

References

GitHub Advisory / Wiki ADVISORY

https://github.com/axios/axios/security/advisories/GHSA-62hf-57xw-28j9

NVD — CVE-2026-42039 NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-42039

Security Fix Commit FIX COMMIT

https://github.com/axios/axios/commit/85132ffba1a77609ea5d101c8a413dea7174932f

Axios Source Repository REPOSITORY

https://github.com/axios/axios

Axios Release RELEASE

https://github.com/axios/axios/releases/tag/v1.15.1

Frequently Asked Questions

What is CVE-2026-42039?

CVE-2026-42039 is a security vulnerability in Axios involving unbounded recursion in toFormData causes DoS via deeply nested request data under CWE-674: Uncontrolled Recursion.

Which Axios versions are affected?

Affected versions include releases prior to 1.15.1, 0.31.1 across affected packages: axios.

What version fixes CVE-2026-42039?

Upgrading to 1.15.1, 0.31.1 (or the latest patched release for your respective branch) resolves the vulnerability.

Is axios affected?

Yes, axios is affected in releases prior to 1.15.1, 0.31.1. Upgrade your dependency to 1.15.1, 0.31.1 or later.

What is the CVSS score of CVE-2026-42039?

CVE-2026-42039 has a CVSS v3.1 base score of 7.5 (MODERATE) 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-2026-42039?

CVE-2026-42039 is classified under CWE-674: Uncontrolled Recursion (The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.).

How can I check npm dependencies for CVE-2026-42039?

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-62hf-57xw-28j9",
  "modified" : "2026-06-08T15:54:28Z",
  "published" : "2026-05-05T00:34:32Z",
  "aliases" : [ "CVE-2026-42039" ],
  "summary" : "Axios: unbounded recursion in toFormData causes DoS via deeply nested request data",
  "details" : "### Summary\ntoFormData recursively walks nested objects with no depth limit, so a deeply nested value passed as request data crashes the Node.js process with a RangeError.\n\n### Details\nlib/helpers/toFormData.js:210 defines an inner `build(value, path)` that recurses into every object/array child (line 225: `build(el, path ? path.concat(key) : [key])`). The only safeguard is a `stack` array used to detect circular references; there is no maximum depth and no try/catch around the recursion. Because `build` calls itself once per nesting level, a payload nested roughly 2000+ levels deep exhausts V8's call stack.\n\n`toFormData` is the serializer behind `FormData` request bodies and `AxiosURLSearchParams` (used by `buildURL` when `params` is an object with `URLSearchParams` unavailable, see `lib/helpers/buildURL.js:53` and `lib/helpers/AxiosURLSearchParams.js:36`). Any server-side code that forwards a client-supplied object into `axios({ data, params })` therefore reaches the recursive walker with attacker-controlled depth.\n\nThe RangeError is thrown synchronously from inside `forEach`, escapes `toFormData`, and propagates out of the axios request call. In typical Express/Fastify request handlers this terminates the running request; in synchronous startup paths or worker threads it can crash the whole process.\n\n### PoC\n```js\nimport toFormData from 'axios/lib/helpers/toFormData.js';\nimport FormData from 'form-data';\n\nfunction nest(depth) {\n  let o = { leaf: 1 };\n  for (let i = 0; i < depth; i++) o = { a: o };\n  return o;\n}\n\ntry {\n  toFormData(nest(2500), new FormData());\n} catch (e) {\n  console.log(e.name + ': ' + e.message);\n}\n// RangeError: Maximum call stack size exceeded\n```\n\nServer-side reachability example:\n```js\n// vulnerable proxy pattern\napp.post('/forward', async (req, res) => {\n  await axios.post('https://upstream/api', req.body); // req.body user-controlled\n  res.send('ok');\n});\n// attacker POST /forward with {\"a\":{\"a\":{\"a\":... 2500 deep ...}}}\n// -> toFormData build() overflows -> request handler crashes\n```\n\nVerified on axios 1.15.0 (latest, 2026-04-10), Node.js 20, 3/3 PoC runs reproduce the RangeError at depth 2500.\n\n### Impact\nA remote, unauthenticated attacker who can influence an object passed to axios as request `data` or `params` triggers an uncaught RangeError inside the synchronous recursive walker. In server-side applications that proxy or re-send client JSON through axios this crashes the request handler and, in worker/cluster setups, the process. Fix by bounding recursion depth in `toFormData`'s `build` function (reject or throw on depths beyond a configurable limit, e.g. 100) or rewriting the walker iteratively.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "axios"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.0.0"
      }, {
        "fixed" : "1.15.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "axios"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.31.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.31.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/security/advisories/GHSA-62hf-57xw-28j9"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42039"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/commit/85132ffba1a77609ea5d101c8a413dea7174932f"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/axios/axios"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/axios/axios/releases/tag/v1.15.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-674" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-05T00:34:32Z",
    "nvd_published_at" : "2026-04-24T18:16:30Z"
  }
}

CVSS V3

7.5 MODERATE