{"id":"CVE-2026-48525","summary":"PyJWT: Unauthenticated DoS via unbounded Base64URL decoding of unused payload segment in b64=false detached JWS","details":"PyJWT is a JSON Web Token implementation in Python. From 2.8.0 to 2.12.1, when verifying detached JWS tokens using the unencoded-payload option (\"b64\": false, RFC 7797), PyJWT performs Base64URL decoding of the compact-serialization payload segment before enforcing the detached-payload rules. For b64=false, PyJWT later discards that decoded payload and replaces it with the caller-provided detached_payload. In practice, this turns the middle segment into an attacker-controlled “work amplifier”: a remote client can supply an arbitrarily large Base64URL payload segment that forces CPU work + memory allocations even if the signature is invalid. This creates an unauthenticated DoS vector against any endpoint that verifies detached JWS using PyJWT. This vulnerability is fixed in 2.13.0.","aliases":["GHSA-w7vc-732c-9m39","PYSEC-2026-178"],"modified":"2026-06-24T18:29:32.458809978Z","published":"2026-05-28T15:11:12.483Z","related":["CGA-mrfj-xj9f-w374","SUSE-SU-2026:22138-1","SUSE-SU-2026:22170-1","SUSE-SU-2026:22220-1","openSUSE-SU-2026:11024-1"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-400"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48525.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48525.json"},{"type":"ADVISORY","url":"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48525"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/jpadilla/pyjwt","events":[{"introduced":"72ad55f6d7041ae698dc0790a690804118be50fc"},{"fixed":"7144e4534c34810f4525dc4578a32addd8212cff"}],"database_specific":{"source":["AFFECTED_FIELD","CPE_RANGE"],"cpe":"cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"2.8.0"},{"fixed":"2.13.0"},{"introduced":"2.8.0"},{"last_affected":"2.12.1"}]}}],"versions":["2.12.1","2.12.0","2.11.0","2.10.1","2.10.0","2.9.0","2.8.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-48525.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}