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The vulnerability exists in the TokenRequestCache mechanism of the Auth0 Next.js SDK (versions 4.11.0-4.11.1 and 4.12.0). When the SDK processes authentication token requests, it uses a cache to store results and prevent redundant network calls. The cache key is improperly derived, potentially from a non-unique request parameter. During high-concurrency scenarios, two simultaneous authentication requests from the same user session could generate identical cache keys. This causes the second request to perform a cache lookup while the first is still in flight and has not yet populated the cache with the result. The flawed lookup logic may then return a null or stale cached value for the second request, causing it to fail or receive incorrect authentication state. This race condition leads to authentication errors for legitimate user requests.
Platform: Node.js (Next.js)
Version: 4.11.0-4.11.1
Vulnerability : Race Condition
Severity: Moderate
date: 2025-12-10
Prediction: 2025-12-17
What Undercode Say:
npm list nextjs-auth0 Check for vulnerable versions: 4.11.0, 4.11.1, 4.12.0 npm update nextjs-auth0 Upgrade to patched version: 4.11.2 or 4.12.1
How Exploit:
An attacker cannot directly trigger this flaw, but can exploit it indirectly. By scripting a client to send multiple concurrent authentication requests (e.g., rapid page refreshes, simultaneous API calls), they increase the likelihood of triggering the race condition. This causes authentication failures for the legitimate user, leading to denial of service for their session or inconsistent application state.
Protection from this CVE
Upgrade SDK immediately. Apply patched versions. Review authentication logs.
Impact:
Authentication failures for users. Session inconsistency. Denial of service.
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Sources:
Reported By: github.com
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