UBUNTU-CVE-2026-48523

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.

References

Affected packages

Ubuntu:25.10 / pyjwt

Package

Name: pyjwt
Purl: pkg:deb/ubuntu/pyjwt?arch=source&distro=questing

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0 Unknown introduced version / All previous versions are affected

Affected versions

2.*

2.10.1-2

2.10.1-2ubuntu0.1

Ecosystem specific

{
    "binaries":  [
        {
            "binary_name":  "python3-jwt",
            "binary_version":  "2.10.1-2ubuntu0.1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48523.json"

Ubuntu:26.04:LTS / pyjwt

Package

Name: pyjwt
Purl: pkg:deb/ubuntu/pyjwt?arch=source&distro=resolute

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0 Unknown introduced version / All previous versions are affected

Fixed

2.10.1-4ubuntu1.1

Affected versions

2.*

2.10.1-2

2.10.1-3

2.10.1-3build1

2.10.1-4

2.10.1-4ubuntu1

Ecosystem specific

{
    "availability":  "No subscription required",
    "binaries":  [
        {
            "binary_name":  "python3-jwt",
            "binary_version":  "2.10.1-4ubuntu1.1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48523.json"