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

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.

Problem type

Affected products

jpadilla

pyjwt

< 2.13.0 - AFFECTED

References

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

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

x_refsource_CONFIRM

JSON source

https://cveawg.mitre.org/api/cve/CVE-2026-48524

Click to expand

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