{"id":"PYSEC-2026-178","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":["CVE-2026-48525","GHSA-w7vc-732c-9m39"],"modified":"2026-06-02T12:15:10.739334903Z","published":"2026-05-28T16:16:29.533Z","references":[{"type":"EVIDENCE","url":"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39"}],"affected":[{"package":{"name":"pyjwt","ecosystem":"PyPI","purl":"pkg:pypi/pyjwt"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.8.0"},{"fixed":"2.13.0"}]}],"versions":["2.10.0","2.10.1","2.11.0","2.12.0","2.12.1","2.8.0","2.9.0"],"ecosystem_specific":{},"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/pyjwt/PYSEC-2026-178.yaml"}}],"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"}]}