Vulnerability record · CVE-2026-18500 · published 15 August 2026
CVE-2026-18500: Fastify\/jwt improper verification of cryptographic signature vulnerability
Fastify · Fastify\/Jwt
@fastify/jwt is a JSON Web Token plugin for Fastify. In versions before 10.2.2, a per-request verification key passed to request.jwtVerify({ key }) is silently overridden by the plugin's globally configured secret, because the option merge applies the global key last. Applications that use different keys for different authorization domains, for example separate user and admin keys, therefore accept a token signed with the global key on a route that explicitly requires another key. This lets an ordinary authenticated user cross a key-based trust boundary without knowing either secret. The issue is fixed in @fastify/jwt 10.2.2, where an explicit per-call key takes precedence over the global secret. Users should upgrade to 10.2.2.
Description
@fastify/jwt is a JSON Web Token plugin for Fastify. In versions before 10.2.2, a per-request verification key passed to request.jwtVerify({ key }) is silently overridden by the plugin's globally configured secret, because the option merge applies the global key last. Applications that use different keys for different authorization domains, for example separate user and admin keys, therefore accept a token signed with the global key on a route that explicitly requires another key. This lets an ordinary authenticated user cross a key-based trust boundary without knowing either secret. The issue is fixed in @fastify/jwt 10.2.2, where an explicit per-call key takes precedence over the global secret. Users should upgrade to 10.2.2.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Affected products
1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.
References
| Link | Tags |
|---|---|
| https://cna.openjsf.org/security-advisories.html | Vendor Advisory |
| https://github.com/fastify/fastify-jwt/security/advisories/GHSA-j4cx-787j-xjqg | MitigationVendor Advisory |
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Related vulnerabilities
Same products first, then exploited flaws of the same weakness class.
Source: NIST National Vulnerability Database (record CVE-2026-18500), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.
