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.decodecomplete() 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.getsigningkeyfrom_jwt(...) flow. This vulnerability is fixed in 2.13.0.

Database specific

{
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-347"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48523.json"
}

References

Affected packages

Git / github.com/jpadilla/pyjwt

Affected ranges

Type

GIT

Repo

https://github.com/jpadilla/pyjwt

Events

Introduced

868cf4ab2ca5a0a39da40e5a14dd740b203662b2

Fixed

7144e4534c34810f4525dc4578a32addd8212cff

Database specific

{
    "cpe": "cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:*",
    "source": [
        "AFFECTED_FIELD",
        "CPE_RANGE"
    ],
    "extracted_events": [
        {
            "introduced": "2.9.0"
        },
        {
            "fixed": "2.13.0"
        },
        {
            "introduced": "2.9.0"
        },
        {
            "fixed": "2.12.1"
        }
    ]
}

Affected versions

2.*

2.10.0

2.10.1

2.11.0

2.12.0

2.12.1

2.9.0

Database specific

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-48523.json"