CVE-2026-23996FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection

Official description

FastAPI Api Key provides a backend-agnostic library that provides an API key system. Version 1.1.0 has a 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. All users relying on verify_key() for API key authentication prior to the fix are affected. Users should upgrade to version 1.1.0 to receive a patch. The patch applies a uniform random delay (min_delay to max_delay) to all responses regardless of outcome, eliminating the timing correlation. Some workarounds are available. Add an application-level fixed delay or random jitter to all authentication responses (success and failure) before the fix is applied and/or use rate limiting to reduce the feasibility of statistical timing attacks.

Affected packages & fixed versions

Affected products (as reported)

References

• https://github.com/Athroniaeth/fastapi-api-key/security/advisories/GHSA-95c6-p277-p87g x_refsource_CONFIRM
• https://github.com/Athroniaeth/fastapi-api-key/commit/310b2c5c77305f38c63c0b917539a0344071dfd8 x_refsource_MISC
• https://github.com/Athroniaeth/fastapi-api-key/releases/tag/1.1.0 x_refsource_MISC