{"cve":"CVE-2026-102266","nvd":{"published":"2026-09-28T21:17:14.257","modified":"2026-10-07T20:55:07.653","status":"Analyzed","description":"PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.from_jwk is affected because PyJWK verification path used the decoded key without applying prepare_key validation. This occurs when a trusted JWK Set contains an oct entry with an empty k value. As a result, an attacker signs an HMAC token with the same zero-length key accepted by PyJWT. Consequently, forged token can carry arbitrary authenticated claims. This issue is fixed in version 2.14.0.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","score":9.1},"cwes":["CWE-347"],"references":["https://github.com/jpadilla/pyjwt/commit/f91ed44dd65baaf457f4b3353ed35e98a753934c","https://github.com/jpadilla/pyjwt/releases/tag/2.14.0","https://github.com/jpadilla/pyjwt/security/advisories/GHSA-9j54-fg26-wv3r","https://github.com/jpadilla/pyjwt/security/advisories/GHSA-9j54-fg26-wv3r"],"products":["pyjwt_project:pyjwt"],"source":"nvd","synced_at":"2026-10-19T22:56:48.555445741+00:00"},"epss":{"cve":"CVE-2026-102266","score":0.00225,"percentile":0.13005,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-9j54-fg26-wv3r","url":"https://osv.dev/vulnerability/GHSA-9j54-fg26-wv3r","summary":"PyJWT: PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation","modified":"2026-10-01T17:56:01.035847258Z","packages":[{"ecosystem":"PyPI","name":"pyjwt","purl":"pkg:pypi/pyjwt","ranges":[">=2.13.0 <2.14.0"],"fixed":["2.14.0"]}]},{"id":"PYSEC-2026-4143","url":"https://osv.dev/vulnerability/PYSEC-2026-4143","summary":"PyJWT: PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation","modified":"2026-10-01T17:45:15.998111810Z","packages":[{"ecosystem":"PyPI","name":"pyjwt","purl":"pkg:pypi/pyjwt","ranges":[">=2.13.0 <2.14.0"],"fixed":["2.14.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}