CVE-2026-48523
Publication date 28 May 2026
Last updated 6 June 2026
Ubuntu priority
Description
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 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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| pyjwt | 26.04 LTS resolute |
Needs evaluation
|
| 25.10 questing |
Needs evaluation
|
|
| 24.04 LTS noble |
Needs evaluation
|
|
| 22.04 LTS jammy |
Needs evaluation
|
|
| 20.04 LTS focal |
Needs evaluation
|
|
| 18.04 LTS bionic |
Needs evaluation
|
|
| 16.04 LTS xenial |
Needs evaluation
|
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
5.4 · Medium
|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | Low |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | Low |
| Integrity impact | Low |
| Availability impact | None |
| Vector | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N |