CVE-2026-48524

PyJWT: PyJWKClient unbounded JWKS endpoint requests via attacker-controlled kid values (DoS)

State: Published
Severity: 3.7 Low
Published: May 28, 2026
Updated: May 28, 2026
Reserved: May 21, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
3.1	3.7 Low	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L	GitHub_M

Weaknesses

CWE-460 Improper Cleanup on Thrown Exception
CWE-755 Improper Handling of Exceptional Conditions

Affected Products

Product	Versions
pyjwtjpadilla	< 2.13.0Affected

References

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

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.