CVE-2026-18500
HighCVSS 8.1Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
In @fastify/jwt, a JSON Web Token plugin for Fastify, 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. Applications using different keys for different authorization domains may accept tokens signed with the global key on routes requiring another key, allowing an ordinary authenticated user to cross a key-based trust boundary. The issue is fixed in version 10.2.2.
Risk Assessment
The risk includes potential unauthorized access to resources protected by a different key, leading to authorization integrity breach.
Recommendation
It is recommended to upgrade @fastify/jwt to version 10.2.2 or later.
Original NVD description (English source)
@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.