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 Types
| Type | CWE ID | Description |
|---|
| CWE | CWE-460 | CWE-460: Improper Cleanup on Thrown Exception |
| CWE | CWE-755 | CWE-755: Improper Handling of Exceptional Conditions |
Type: CWE
Description: CWE-460: Improper Cleanup on Thrown Exception
Type: CWE
Description: CWE-755: Improper Handling of Exceptional Conditions
Metrics
| Version | Base score | Base severity | Vector |
|---|
| 3.1 | 3.7 | LOW | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L |
Version: 3.1
Base score: 3.7
Base severity: LOW
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L