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.
Fix
Patch, vendor advisory and mitigation references on NVD 2
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 Exploit, Mitigation, Vendor Advisory
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 Exploit, Mitigation, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 5.3 · pyjwt_projectNVD modified 2026-10-25 23:10
Affected (CPE criteria) 1
cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:*
References 2
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 Exploit, Mitigation, Vendor Advisory
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 Exploit, Mitigation, Vendor Advisory