CVE-2025-59936
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-09-27

Last updated on: 2025-09-29

Assigner: GitHub, Inc.

Description
get-jwks contains fetch utils for JWKS keys. In versions prior to 11.0.2, a vulnerability in get-jwks can lead to cache poisoning in the JWKS key-fetching mechanism. When the iss (issuer) claim is validated only after keys are retrieved from the cache, it is possible for cached keys from an unexpected issuer to be reused, resulting in a bypass of issuer validation. This design flaw enables a potential attack where a malicious actor crafts a pair of JWTs, the first one ensuring that a chosen public key is fetched and stored in the shared JWKS cache, and the second one leveraging that cached key to pass signature validation for a targeted iss value. The vulnerability will work only if the iss validation is done after the use of get-jwks for keys retrieval. This issue has been patched in version 11.0.2.
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Meta Information
Published
2025-09-27
Last Modified
2025-09-29
Generated
2026-06-16
AI Q&A
2025-09-27
EPSS Evaluated
2026-06-15
NVD
CVE-2025-59936
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
nearform get-jwks 11.0.1
nearform get-jwks 11.0.2
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-116 The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.
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Executive Summary

The vulnerability in get-jwks prior to version 11.0.2 involves cache poisoning in the JWKS key-fetching mechanism. Specifically, if the issuer (iss) claim is validated only after keys are retrieved from the cache, cached keys from an unexpected issuer can be reused. This allows an attacker to craft two JWTs: the first causes a chosen public key to be stored in the shared JWKS cache, and the second uses that cached key to pass signature validation for a targeted issuer value, effectively bypassing issuer validation.

Impact Analysis

This vulnerability can allow an attacker to bypass issuer validation by reusing cached keys from an unexpected issuer. This means that an attacker could potentially authenticate as a different issuer, leading to unauthorized access or actions within systems relying on get-jwks for JWT validation.

Mitigation Strategies

Upgrade get-jwks to version 11.0.2 or later, where the vulnerability has been patched. Additionally, ensure that the iss (issuer) claim validation is performed before retrieving keys from the JWKS cache to prevent cache poisoning attacks.

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