CVE-2025-59936: Improper Encoding (CVSS 9.4)

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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CVSS v3.1 Score

9.4

CRITICAL

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Weakness Type (CWE)

CWE-116 CWE-116

References

Other References

https://github.com/nearform/get-jwks/commit/1706a177a80a1759fe68e3339dc5a219ce03ddb9 https://github.com/nearform/get-jwks/security/advisories/GHSA-qc2q-qhf3-235m

Frequently Asked Questions

What is CVE-2025-59936? +

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. It has a CVSS v3.1 base score of 9.4 (CRITICAL).

How severe is CVE-2025-59936? +

CVE-2025-59936 has a CVSS v3.1 score of 9.4 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately.

How do I check if I'm vulnerable to CVE-2025-59936? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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