CVE-2026-42035: Axios: Header Injection via Prototype Pollution

Vulnerability summary

CVE-2026-42035 is a high (CVSS 7.4) vulnerability in axios. EPSS estimates a 0.40% chance of exploitation in the next 30 days, higher than 34.5% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 24-04-2026
   PublishedVulnerability first disclosed.
2. 25-04-2026
   Last modifiedVulnerability information updated.

Description

Axios is a promise based HTTP client for the browser and Node.js. Prior to 1.15.1 and 0.31.1, a prototype pollution gadget exists in the Axios HTTP adapter (lib/adapters/http.js) that allows an attacker to inject arbitrary HTTP headers into outgoing requests. The vulnerability exploits duck-type checking of the data payload, where if Object.prototype is polluted with getHeaders, append, pipe, on, once, and Symbol.toStringTag, Axios misidentifies any plain object payload as a FormData instance and calls the attacker-controlled getHeaders() function, merging the returned headers into the outgoing request. The vulnerable code resides exclusively in lib/adapters/http.js. The prototype pollution source does not need to originate from Axios itself — any prototype pollution primitive in any dependency in the application's dependency tree is sufficient to trigger this gadget. This vulnerability is fixed in 1.15.1 and 0.31.1.

• CWE-113Improper Neutralization of CRLF Sequences in HTTP HeadersThe product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes CR and LF characters before the data is included in outgoing HTTP headers.
• CWE-1321Improperly Controlled Modification of Object Prototype AttributesThe 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.