Quick answers
- Is CVE-2026-18500 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-18500 being exploited in the wild.
- How severe is CVE-2026-18500?
- High severity, with a CVSS score of 8.1, published 15 August 2026.
- Which products and versions are affected?
- OpenJS Foundation @Fastify/Jwt < 10.2.2.
- Is there a fix for CVE-2026-18500?
- A patch was published on 2026-08-15: Version 10.2.2 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-18500 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-18500?
- Check whether you run OpenJS Foundation @Fastify/Jwt at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
This is an improper cryptographic signature verification vulnerability (CWE-347) in @fastify/jwt versions before 10.2.2. The root cause is that the plugin's option merge logic applies the global secret last, overriding any per-request key explicitly passed to request.jwtVerify({ key }) or reply.jwtSign(payload, { key }). An authenticated attacker with a token signed using the global secret can exploit this to bypass authorization checks on routes designed to accept only tokens signed with a different key. The vulnerability requires the attacker to be already authenticated (low privilege) but no user interaction or out-of-band information about the target key is needed. The attack vector is network-based. Direct verification using fastify.jwt.verify(token, { key }) is not affected. The issue is fixed in version 10.2.2, where per-call keys take precedence over global secrets.
Affected products
- OpenJS Foundation @fastify/jwt < 10.2.2
Timeline
- 2026-08-14: disclosed
- 2026-08-15: advisory
- 2026-08-15: patched: Version 10.2.2 released