Axios CVE-2026-42035

Two prerequisites must be satisfied: (1) Object.prototype pollution primitive must exist somewhere in the application's dependency tree-this can originate from any vulnerable library (lodash merge/defaultsDeep misuse, jQuery extend, etc.), not necessarily Axios itself; (2) Application must use the Node.js HTTP adapter in lib/adapters/http.js to make requests with plain object payloads (browser usage via XMLHttpRequest/fetch adapters is not vulnerable). The pollution must specifically include getHeaders (function), append, pipe, on, once (arbitrary truthy values), and Symbol.toStringTag (set to 'FormData'). Attack complexity is HIGH (CVSS AC:H) because the attacker must first discover and exploit the separate prototype pollution vulnerability. No authentication or user interaction required once prerequisites are met (PR:N/UI:N). Exploitation limited to Node.js server-side environments; browser-based Axios usage unaffected.

CVSS 7.4 (High) reflects network attack vector with high attack complexity (AV:N/AC:H/PR:N/UI:N), high confidentiality and integrity impact, but no availability impact. The AC:H rating indicates the attacker must first achieve prototype pollution through another vulnerability-this is a second-order exploitation requiring a pollution primitive elsewhere in the codebase. Real-world risk depends heavily on application context: applications with known prototype pollution vulnerabilities in dependencies (common in Node.js ecosystems) face immediate risk, while hardened applications with prototype pollution mitigations have lower exposure. The PR:N (no privileges required) and UI:N (no user interaction) components indicate exploitation can be fully automated once the prerequisite pollution exists. No EPSS score provided limits quantitative exploitation probability assessment. CISA KEV status is negative, suggesting no widespread active exploitation detected. However, GitHub security advisory confirms exploit details are public, enabling targeted attacks. SSVC framework assessment: Exploitation=POC (public code available), Automatable=Yes (given pollution prerequisite), Technical Impact=Partial (header injection enables multiple attack vectors). Priority should be HIGH for Node.js applications with complex dependency trees, MEDIUM for applications with prototype pollution hardening.

An attacker identifies a Node.js web application using Axios 1.14.0 that also has a prototype pollution vulnerability in a dependency like lodash 4.17.20. The attacker sends a crafted JSON payload (e.g., {"__proto__": {"getHeaders": "<malicious function>", "append": true, "pipe": true, "on": true, "once": true, "[Symbol.toStringTag]": "FormData"}}) to pollute Object.prototype. When the application subsequently uses Axios to make an outbound API request with a plain object payload, Axios misidentifies the payload as FormData, executes the attacker's getHeaders() function, and injects attacker-controlled headers (e.g., "Authorization: Bearer stolen_token") into the HTTP request. This enables session hijacking, privilege escalation, or cache poisoning depending on the target API's header processing.