{"schemaVersion":3,"id":"CVE-2026-33808","aliases":["GHSA-6hw5-45gm-fj88"],"status":"published","duplicateOf":null,"title":null,"description":"Impact@fastify/express v4.0.4 and earlier fails to normalize URLs before passing them to Express middleware when Fastify router normalization options are enabled. This allows complete bypass of path-scoped authentication middleware via duplicate slashes when ignoreDuplicateSlashes is enabled, or via semicolon delimiters when useSemicolonDelimiter is enabled. In both cases, Fastify router normalizes the URL and matches the route, but @fastify/express passes the original un-normalized URL to Express middleware, which fails to match and is skipped. An unauthenticated attacker can access protected routes by manipulating the URL path.\n\nPatchesUpgrade to @fastify/express v4.0.5 or later.","dates":{"published":"2026-04-15T09:29:46.091Z","modified":"2026-04-15T13:10:24.054Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":9.1,"severity":"critical","version":"4.0","versionLabel":"v4.0","source":"CVE.org","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"4.0","versionLabel":"v4.0","source":"CVE.org","score":9.1,"severity":"critical","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":false},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Npm","score":9.1,"severity":"critical","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Npm","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":10,"impact":8.7,"computed":true},{"version":"4.0","versionLabel":"v4.0","source":"NVD","score":9.1,"severity":"critical","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","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":0.00551,"percentile":0.45249,"severity":"low","asOf":"2026-10-21T00:00:00.000Z","change":{"pp":0.068,"baselineDate":"2026-09-21T00:00:00.000Z","baselineScore":0.00483},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00551,"percentile":0.45249}],"last30":[{"date":"2026-09-21T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00483,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00551,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00551,"percentile":0.45249}]},"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":[{"id":"GITHUB_FASTIFY_FASTIFY-EXPRESS","name":"Fastify Express","source":"github","url":"https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c","maturity":"poc","reliabilityScore":0.3,"verified":false,"type":null,"platforms":[],"requiresAuth":null,"exploitdb":null,"metasploit":null}],"exploitCount":1,"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","product":"fastify\\/express","name":"fastify\\/express","label":"fastify\\/express","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 4.0.5","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 4.0.5","eol":null,"hubHref":"/vendor/fastify/fastifyexpress"},{"vendor":"@fastify","product":"express","name":"@fastify/express","label":"express","ecosystem":"Npm","cpePart":null,"purl":"pkg:npm/@fastify/express","purlType":"npm","versions":[{"text":"< 4.0.5","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 4.0.5","eol":null,"hubHref":null}],"affectedCount":2,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/fastify/fastify-express/security/advisories/GHSA-6hw5-45gm-fj88","label":"github.com/fastify/fastify-express/security/advisories/GHSA-6hw5-45gm-fj88","hostname":"github.com","tags":["WEB","Exploit","Mitigation","Vendor Advisory"]},{"url":"https://cna.openjsf.org/security-advisories.html","label":"cna.openjsf.org/security-advisories.html","hostname":"cna.openjsf.org","tags":["WEB","Vendor Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33808","label":"nvd.nist.gov/vuln/detail/CVE-2026-33808","hostname":"nvd.nist.gov","tags":["Advisory"]},{"url":"https://github.com/fastify/fastify-express","label":"github.com/fastify/fastify-express","hostname":"github.com","tags":["PACKAGE"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-04-15T09:29:46.091Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-04-15T13:10:24.054Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":70,"level":"high","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-21T16:37:08.309Z","stale":false,"partial":false}}