{"id":"CVE-2026-23996","aliases":["GHSA-95c6-p277-p87g","PYSEC-2026-1358"],"url":"https://o3.security/vulnerability/CVE-2026-23996","summary":"FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection","details":"### Impact\nTiming 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.\n\nAffected: all users relying on verify_key() for API key authentication prior to the fix.\n\n### Patches\nYes. 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.\n\n### Workarounds\n- Add an application-level fixed delay or random jitter to all authentication responses (success and failure) before the fix is applied.\n- Use rate limiting to reduce the feasibility of statistical timing attacks.\n\n### References\n- CWE-208: Observable Timing Discrepancy\n- Commit: 87b27640f77c5ef86c46311b6b5a7e2887e35b77\n- OWASP: https://owasp.org/www-community/attacks/Timing_attack","published":"2026-01-21T22:29:24.107Z","modified":"2026-10-28T02:30:29.984507134Z","cvss":{"score":3.7,"severity":"LOW","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"fastapi-api-key","fixedVersion":"1.1.0"}],"fix":{"url":"https://github.com/Athroniaeth/fastapi-api-key/commit/310b2c5c77305f38c63c0b917539a0344071dfd8","label":"Athroniaeth/fastapi-api-key@310b2c5"},"references":[{"type":"WEB","url":"https://github.com/Athroniaeth/fastapi-api-key/releases/tag/1.1.0"},{"type":"ADVISORY","url":"https://github.com/Athroniaeth/fastapi-api-key/security/advisories/GHSA-95c6-p277-p87g"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23996.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23996"},{"type":"FIX","url":"https://github.com/Athroniaeth/fastapi-api-key/commit/310b2c5c77305f38c63c0b917539a0344071dfd8"},{"type":"PACKAGE","url":"https://github.com/Athroniaeth/fastapi-api-key"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:29.984507134Z"}}