Axios: Proxy-Authorization Header Injection via Prototype Pollution — Incomplete Null-Prototype Fix

CVE-2026-44489

What is CVE-2026-44489?

Axios is a promise based HTTP client for the browser and Node.js. From 1.15.2 to before 1.16.0, nested objects created by utils.merge() (e.g., config.proxy) are still constructed as plain {} with Object.prototype in their chain. The setProxy() function at lib/adapters/http.js:209-223 reads proxy.username, proxy.password, and proxy.auth without hasOwnProperty checks. When Object.prototype.username is polluted, setProxy() constructs a Proxy-Authorization header with attacker-controlled credentials and injects it into every proxied HTTP request. This vulnerability is fixed in 1.16.0.

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