CVE-2026-48524

PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting. Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests. The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker's control. This vulnerability is fixed in 2.13.0.

CVSS 3.1

3.7CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

0.4% chance of exploitation in the next 30 days; higher than 33% of CVEs (scores of 2026-10-25)

CWEs

CWE-460, CWE-755

Published

2026-05-28

Modified

2026-10-26

Record from

the NVD, synced 2026-10-26

Affected

• pyjwt_project:pyjwt

Packages (OSV)

References

• https://github.com/jpadilla/pyjwt/security/advisories/GHSA-fhv5-28vv-h8m8

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