CVE-2026-23996Low· 3.7▾ SunlitFastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection
▾ Sunlit zone — Low / medium · no exploitation signal
impact 20.4 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 8.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
0.3%
0.3% → 0.3%
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.
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.
fastapi-api-key < 1.1.0Upgrade to a patched release:
fastapi-api-key 1.1.0