Affected: npm: axios

# Vulnerability Disclosure: Authentication Bypass via Prototype Pollution Gadget in `validateStatus` Merge Strategy

## Summary

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.

**Severity:** High (CVSS 8.2) **Affected Versions:** All versions (v0.x - v1.x including v1.15.0) **Vulnerable Component:** `lib/core/mergeConfig.js` (`mergeDirectKeys` strategy) + `lib/core/settle.js`

## CWE

- **CWE-1321:** Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') - **CWE-287:** Improper Authentication

## CVSS 3.1

**Score: 8.2 (High)**

Vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N`

| Metric | Value | Justification | |---|---|---| | Attack Vector | Network | PP is triggered remotely | | Attack Complexity | Low | Once PP exists, a single property assignment exploits this. Consistent with GHSA-fvcv-3m26-pcqx | | Privileges Required | None | No au…