Axios: Two Vulnerabilities Allow Header and Socket Hijacking via Prototype Pollution Gadgets

What happened

Two distinct advisories describe how axios's internal request handling can resolve properties inherited from Object.prototype instead of properties explicitly set on a request configuration object. In CVE-2026-101904, the dispatchRequest function normalizes headers and can pick up an inherited 'headers' property placed on Object.prototype, even after trusted request interceptors have returned a clean configuration object. This can expose attacker-controlled header values, including authorization-related data, to downstream request processing. In CVE-2026-101905, the Node HTTP adapter (lib/adapters/http.js) can resolve an inherited 'createConnection' function from Object.prototype when request options do not define their own createConnection value. Node then invokes this inherited function as the socket factory, letting an attacker-controlled function choose the actual network endpoint the request connects to, while the request's URL continues to appear legitimate.

Technical cause

Both issues depend on a separate, same-process prototype-pollution flaw that sets a property (headers or createConnection) on Object.prototype. Axios itself does not pollute the prototype; rather, once Object.prototype has been polluted by another component or code path running in the same process, axios's normalization and adapter logic fails to distinguish between a configuration object's own properties and properties inherited through the prototype chain. CVE-2026-101904 is classified as CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component). CVE-2026-101905 is classified as CWE-441 (Unintended Proxy or Intermediary / 'Confused Deputy').

Why it matters

CVE-2026-101904 carries a CVSS score of 6.9 and can result in attacker-controlled HTTP headers, including authorization-related values, reaching downstream systems. CVE-2026-101905 carries a CVSS score of 7.6 and is more severe in impact: it allows an attacker-controlled function to redirect the actual network connection to an endpoint of the attacker's choosing, letting that endpoint observe request headers and bodies (including credentials) and return fabricated responses, all while the request's intended URL appears unchanged. Both issues require a separate prototype-pollution condition to exist in the same process as a precondition; axios's flaw is in how it fails to guard against inherited properties once that precondition is met.

Affected versions

CVE-2026-101904 affects axios from version 1.0.0 up to, but not including, 1.20.0. CVE-2026-101905 affects axios from version 1.15.2 up to, but not including, 1.20.0. Both issues are fixed in axios 1.20.0.

Fixes and mitigation

Both vulnerabilities are fixed in axios 1.20.0. The fact package does not provide details on what specific code changes were made in the fix beyond the version number. There is no information provided on alternative mitigations for environments that cannot immediately upgrade.

Recommended action

Upgrade axios to version 1.20.0 or later. Because both vulnerabilities require a separate prototype-pollution condition elsewhere in the same process to be exploitable, organizations should also review their dependency tree and application code for any component capable of writing to Object.prototype, as that is the underlying precondition enabling both issues.