Executive brief
Axios is a widely-used HTTP client library for Node.js and browsers. A vulnerability in the Node.js HTTP adapter allows attackers who have polluted the global Object.prototype to intercept and redirect HTTP requests through an attacker-controlled proxy server. When request interceptors clone the configuration object, the protection against prototype pollution is bypassed, enabling the proxy to observe sensitive data like Authorization headers, request bodies, and other metadata—without requiring HTTPS protection.
Technical details
The vulnerability is a prototype pollution bypass in axios' Node.js HTTP adapter. Axios initially hardens merged request config by creating a null-prototype object (lib/core/mergeConfig.js), but request interceptors run after this merge and may return a cloned config using patterns like {...config} or Object.assign({}, config), which converts it back to a normal prototype-inheriting object. The dispatch phase (lib/core/dispatchRequest.js) does not re-harden this object before passing it to the adapter. The Node HTTP adapter (lib/adapters/http.js) then reads config.proxy through the prototype chain, allowing an attacker who has polluted Object.prototype.proxy elsewhere in the process to redirect plaintext HTTP requests through an attacker-controlled proxy. The proxy can observe Authorization headers, Basic auth credentials, request method, absolute URL, Host header, and request body. HTTPS requests with normal TLS validation are not affected. Patches are available in versions >=0.33.0 and >=1.18.0.
Affected products
- axios axios >=0.31.1 <0.33.0, >=1.15.2 <1.18.0
Timeline
- 2026-07-06: disclosed
- 2026-07-20: advisory
- 2026-07-20: patched: Patches available in axios >=0.33.0 and >=1.18.0