low3.7

CVE-2026-23996

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

Impact

### 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

Affected packages

Ecosystem	Package	Affected	Fixed in
pip	`fastapi-api-key`	< 1.1.0	1.1.0

Affected products

Vendor	Product	Affected versions
Athroniaeth	Fastapi Api Key	before 1.1.0

Weakness classification

CWE-208