CVE-2026-42041: Axios: Authentication Bypass via Prototype Pollution Gadget in `validateStatus` Merge Strategy

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-24 · updated 2026-09-10
Weakness: CWE-287

Description

Axios is a promise based HTTP client for the browser and Node.js. Prior to 1.15.1 and 0.31.1, the Axios library is vulnerable to a Prototype Pollution "Gadget" attack that allows any Object.prototype pollution to silently suppress all HTTP error responses (401, 403, 500, etc.), causing them to be treated as successful responses. This completely bypasses application-level authentication and error handling. The root cause is that validateStatus is the only config property using the mergeDirectKeys merge strategy, which uses JavaScript's in operator — an operator that inherently traverses the prototype chain. When Object.prototype.validateStatus is polluted with () => true, all HTTP status codes are accepted as success. This vulnerability is fixed in 1.15.1 and 0.31.1.

Affected products

axios: before 0.31.1; from 1.0.0 before 1.15.1 — fixed in 0.31.1, 1.15.1
Npm Axios: from 1.0.0 before 1.15.1; before 0.31.1 — fixed in 1.15.1, 0.31.1

How to fix

Upgrade to a fixed version: axios 0.31.1, 1.15.1; Npm Axios 1.15.1, 0.31.1. Check the vendor advisory for mitigations.

References

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