EUVD-2026-59757Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Network-exploitable by any authenticated token holder (PR:L); AC:L because no special conditions beyond targeting a multi-key route; no availability impact applies.
Primary rating from Vendor (ce714d77-add3-4f53-aff5-83d477b104bb).
CVSS VectorVendor: ce714d77-add3-4f53-aff5-83d477b104bb
Lifecycle Timeline
3DescriptionCVE.org
@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.
AnalysisAI
Key-based authorization bypass in @fastify/jwt before 10.2.2 permits any low-privileged authenticated user holding a token signed by the application's global secret to access routes explicitly restricted to a separate per-request key, silently crossing a cryptographic trust boundary. Applications implementing multi-domain JWT authorization - for example, separating user and admin token verification keys - are specifically at risk, as the plugin's option merge incorrectly applies the global key last, overriding the developer-supplied per-request key. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires two specific conditions to be met simultaneously: the target application must run @fastify/jwt at any version below 10.2.2, AND it must implement per-request key differentiation by passing a `key` argument to `request.jwtVerify({ key })` on at least one route. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 8.1 score (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N) accurately characterizes risk for the subset of deployments affected, though the realistic attack surface is meaningfully narrower than the score alone implies - only applications explicitly calling `request.jwtVerify({ key })` with a per-request override are vulnerable, making single-key deployments entirely immune. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade @fastify/jwt to version 10.2.2, the confirmed patched release per the vendor security advisory at https://github.com/fastify/fastify-jwt/security/advisories/GHSA-j4cx-787j-xjqg. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all applications using @fastify/jwt and identify those implementing separate security keys for user and administrator roles. …
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