{"id":"CVE-2026-48523","title":"PyJWT is a JSON Web Token implementation in Python","summary":"PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked agains…","severity":"medium","cvss":5.4,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","cwe":["CWE-347"],"vendor":"pyjwt_project","product":"pyjwt","affected":["pyjwt >= 2.9.0, < 2.13.0"],"patched":["pyjwt 2.13.0"],"published":"2026-05-28","updated":"2026-09-16","sourceUpdated":"2026-09-16T20:16:33.817","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-48523","references":[{"url":"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f","label":"security-advisories@github.com"},{"url":"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48523"},{"url":"https://github.com/jpadilla/pyjwt"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-176.yaml"},{"url":"https://github.com/advisories/GHSA-jq35-7prp-9v3f"}],"tags":["nvd","osv","pip","ghsa"],"epss":0.00127,"epssPercentile":0.02682,"aliases":["GHSA-jq35-7prp-9v3f","PYSEC-2026-176"],"ecosystem":"pip","ingestedAt":"2026-07-07T15:41:58.720Z","slug":"CVE-2026-48523","body":"## Overview\n\nPyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.\n\n## Affected\n\n- `pyjwt >= 2.9.0, < 2.13.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `pyjwt 2.13.0`\n\n## Package advisory (CVE-2026-48523)\n\nAffected packages:\n\n- `pyjwt >= 2.9.0, < 2.13.0`\n\nPatched in:\n\n- `pyjwt 2.13.0`\n\nSource: https://osv.dev/vulnerability/GHSA-jq35-7prp-9v3f","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":29.7,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}