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.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Redhat_linux | — | No solution exists | Jul 17, 2026 | May 28, 2026 |
| Ubuntu | — | Upgrade python-jwt (Ubuntu Pro)Upgrade python3-jwtUpgrade python3-jwt (Ubuntu Pro) | Sep 28, 2026 | Sep 25, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Sep 15, 2026 | May 28, 2026 |
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