CVE-2026-18500

@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 v3 8.1 HIGH

8.1^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.8 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://cna.openjsf.org/security-advisories.html	Vendor Advisory
https://github.com/fastify/fastify-jwt/security/advisories/GHSA-j4cx-787j-xjqg	Mitigation Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:fastify:fastify\/jwt:*:*:*:*:*:node.js:*:*

History

No history.

Information

Published : 2026-08-15 14:17

Updated : 2026-09-04 13:17

NVD link : CVE-2026-18500

Mitre link : CVE-2026-18500

CVE.ORG link : CVE-2026-18500

JSON object : View

Products Affected

fastify

fastify\/jwt

CWE

CWE-347

Improper Verification of Cryptographic Signature

{"id": "CVE-2026-18500", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-18500", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "version": "2.0.3", "timestamp": "2026-08-17T19:45:28.953645Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "ce714d77-add3-4f53-aff5-83d477b104bb", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 8.1, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}, "impactScore": 5.2, "exploitabilityScore": 2.8}]}, "affected": [{"source": "ce714d77-add3-4f53-aff5-83d477b104bb", "affectedData": [{"vendor": "@fastify/jwt", "product": "@fastify/jwt", "versions": [{"status": "affected", "version": "0", "lessThan": "10.2.2", "versionType": "semver"}, {"status": "unaffected", "version": "10.2.2", "versionType": "semver"}], "packageURL": "pkg:npm/@fastify/jwt", "defaultStatus": "unaffected"}]}], "published": "2026-08-15T14:17:07.473", "references": [{"url": "https://cna.openjsf.org/security-advisories.html", "tags": ["Vendor Advisory"], "source": "ce714d77-add3-4f53-aff5-83d477b104bb"}, {"url": "https://github.com/fastify/fastify-jwt/security/advisories/GHSA-j4cx-787j-xjqg", "tags": ["Mitigation", "Vendor Advisory"], "source": "ce714d77-add3-4f53-aff5-83d477b104bb"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "ce714d77-add3-4f53-aff5-83d477b104bb", "description": [{"lang": "en", "value": "CWE-347"}]}], "descriptions": [{"lang": "en", "value": "@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."}], "lastModified": "2026-09-04T13:17:20.220", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:fastify:fastify\\/jwt:*:*:*:*:*:node.js:*:*", "vulnerable": true, "matchCriteriaId": "E2B7590D-4505-4067-81E5-97513D78FC8C", "versionEndExcluding": "10.2.2"}], "operator": "OR"}]}], "sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb"}