PYSEC-2026-1358
FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection
Details
### Impact Timing side-channel vulnerability in verify_key(). The method applied a random delay only on verification failures, allowing an attacker to statistically distinguish valid from invalid API keys by measuring response latencies. With enough repeated requests, an adversary could infer whether a key_id corresponds to a valid key, potentially accelerating brute-force or enumeration attacks.
Affected: all users relying on verify_key() for API key authentication prior to the fix.
### Patches Yes. Users should upgrade to version 1.1.0 (or the version containing this fix). The patch applies a uniform random delay (min_delay to max_delay) to all responses regardless of outcome, eliminating the timing correlation.
### Workarounds - Add an application-level fixed delay or random jitter to all authentication responses (success and failure) before the fix is applied. - Use rate limiting to reduce the feasibility of statistical timing attacks.
### References - CWE-208: Observable Timing Discrepancy - Commit: 87b27640f77c5ef86c46311b6b5a7e2887e35b77 - OWASP: https://owasp.org/www-community/attacks/Timing_attack
Are you affected?
Enter the version of the package you're using.
Affected packages
0 Fixed in: 1.1.0 pip install --upgrade 'fastapi-api-key>=1.1.0' References
- https://github.com/Athroniaeth/fastapi-api-key/security/advisories/GHSA-95c6-p277-p87g [WEB]
- https://nvd.nist.gov/vuln/detail/CVE-2026-23996 [ADVISORY]
- https://github.com/Athroniaeth/fastapi-api-key/commit/310b2c5c77305f38c63c0b917539a0344071dfd8 [WEB]
- https://github.com/Athroniaeth/fastapi-api-key [PACKAGE]
- https://github.com/Athroniaeth/fastapi-api-key/releases/tag/1.1.0 [WEB]
- https://pypi.org/project/fastapi-api-key [PACKAGE]
- https://github.com/advisories/GHSA-95c6-p277-p87g [ADVISORY]