{"schemaVersion":3,"id":"CVE-2026-112712","aliases":[],"status":"published","duplicateOf":null,"title":null,"description":"@fastify/middie is the Express-style middleware engine for Fastify. In versions from 9.0.0 through 9.3.5, the use() function joined a path-scoped middleware's mount path to the plugin scope prefix in a way that could diverge from the path Fastify's router serves, most often when the scope prefix ended in a slash, and also for array mount paths and for mount paths written without a leading slash. When the two paths disagreed, the middleware was silently skipped while the route handler still ran, so path-scoped middleware such as authentication, authorization, or rate limiting could be bypassed by a single unauthenticated request. The issue is fixed in @fastify/middie 9.3.6, and users should upgrade to 9.3.6 or later. As a workaround, enforce authorization in a Fastify hook such as preHandler that runs after the router has resolved the request.","dates":{"published":"2026-10-20T20:43:48.681Z","modified":"2026-10-20T20:43:48.681Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":9.1,"severity":"critical","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":9.1,"severity":"critical","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":9.1,"severity":"critical","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00314,"percentile":0.23067,"severity":"low","asOf":"2026-10-21T00:00:00.000Z","change":{"pp":null,"baselineDate":null,"baselineScore":null},"history":[{"date":"2026-10-21T00:00:00.000Z","score":0.00314,"percentile":0.23067}],"last30":[{"date":"2026-10-21T00:00:00.000Z","score":0.00314,"percentile":0.23067}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-436","name":"Interpretation Conflict","description":"Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state.","type":"weakness","status":"Incomplete","abstraction":"Class","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/436.html"}],"affected":[{"vendor":"@fastify/middie","product":"@fastify/middie","name":"@fastify/middie","label":"@fastify/middie","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 9.0.0, < 9.3.6","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 9.0.0, < 9.3.6","eol":null,"hubHref":"/vendor/fastifymiddie/fastifymiddie"}],"affectedCount":1,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/fastify/middie/security/advisories/GHSA-5p92-8765-9fv8","label":"github.com/fastify/middie/security/advisories/GHSA-5p92-8765-9fv8","hostname":"github.com","tags":[]},{"url":"https://cna.openjsf.org/security-advisories.html","label":"cna.openjsf.org/security-advisories.html","hostname":"cna.openjsf.org","tags":[]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-10-20T20:43:48.681Z","label":"Published","detail":"Vulnerability first disclosed.","source":null}],"risk":{"score":70,"level":"high","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-21T20:38:48.360Z","stale":false,"partial":false}}