{"id":"CVE-2026-23996","aliases":["EUVD-2026-4139","GHSA-95c6-p277-p87g","PYSEC-2026-1358"],"status":"published","title":"FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection","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.","severity":{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00291,"percentile":0.21915,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-208"],"published":"2026-01-21T22:27:39Z","modified":"2026-10-28T02:30:29Z","fixes":[{"ecosystem":"PyPI","package":"fastapi-api-key","fixed_in":["1.1.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"fastapi-api-key","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.0"}]}]},{"source":"osv","ecosystem":"PyPI","package":"fastapi-api-key","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.0"}]}],"versions":["0.10.0","0.11.0","0.12.0","0.13.0","0.13.1","0.13.2","0.13.3","0.2.1","0.3.0","0.4.0","0.5.0","0.6.0","0.7.1","0.7.2","0.7.3","0.8.0","0.8.1","0.8.2","0.8.3","0.9.0","1.0.0"]},{"source":"osv","ecosystem":"PyPI","package":"fastapi-api-key","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.0"}]}],"versions":["0.10.0","0.11.0","0.12.0","0.13.0","0.13.1","0.13.2","0.13.3","0.2.1","0.3.0","0.4.0","0.5.0","0.6.0","0.7.1","0.7.2","0.7.3","0.8.0","0.8.1","0.8.2","0.8.3","0.9.0","1.0.0"]}],"products":[{"vendor":"athroniaeth","product":"fastapi-api-key"},{"vendor":"athroniaeth","product":"fastapi_api_key"}],"references":[{"url":"https://github.com/Athroniaeth/fastapi-api-key/security/advisories/GHSA-95c6-p277-p87g","tags":["x_refsource_CONFIRM","Mitigation","Patch","Vendor Advisory","advisory","web"]},{"url":"https://github.com/Athroniaeth/fastapi-api-key/commit/310b2c5c77305f38c63c0b917539a0344071dfd8","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/Athroniaeth/fastapi-api-key/releases/tag/1.1.0","tags":["x_refsource_MISC","Product","Release Notes","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23996","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-95c6-p277-p87g","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23996.json","tags":["advisory"]},{"url":"https://github.com/Athroniaeth/fastapi-api-key","tags":["package"]},{"url":"https://pypi.org/project/fastapi-api-key","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-23996","title":"FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection","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.","status":"published","published":"2026-01-21T22:29:24.107Z","modified":"2026-01-22T16:49:16.733Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"cna"}],"cwes":["CWE-208"],"updated_at":"2026-11-02T13:42:15.603999Z"}],"euvd":[{"id":"EUVD-2026-4139","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.","status":"published","published":"2026-01-21T22:29:24Z","modified":"2026-01-22T16:49:16Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"updated_at":"2026-11-02T19:48:48.575559Z"}],"ghsa":[{"id":"GHSA-95c6-p277-p87g","title":"FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection","description":"### 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","status":"published","published":"2026-01-21T22:27:39Z","modified":"2026-01-22T15:40:30Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"cwes":["CWE-208"],"updated_at":"2026-11-02T14:39:18.564331Z"}],"nvd":[{"id":"CVE-2026-23996","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.","status":"published","published":"2026-01-21T23:15:53.09Z","modified":"2026-06-17T10:22:26.95Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"secondary"}],"cwes":["CWE-208"],"updated_at":"2026-11-02T14:12:04.423757Z"}],"osv":[{"id":"CVE-2026-23996","title":"FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection","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.","status":"published","published":"2026-01-21T22:29:24.107Z","modified":"2026-10-28T02:30:29.984507134Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"cwes":["CWE-208"],"updated_at":"2026-11-02T15:44:59.079784Z"},{"id":"GHSA-95c6-p277-p87g","title":"FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection","description":"### 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","status":"published","published":"2026-01-21T22:27:39Z","modified":"2026-07-07T17:57:38.313530202Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"cwes":["CWE-208"],"updated_at":"2026-11-02T15:46:43.123867Z"},{"id":"PYSEC-2026-1358","title":"FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection","description":"### 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","status":"published","published":"2026-07-07T16:03:19.699103Z","modified":"2026-07-07T17:47:35.926091029Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"updated_at":"2026-11-02T15:52:54.622769Z"}]}}