{"cve":"CVE-2026-33808","nvd":{"published":"2026-04-15T10:16:48.453","modified":"2026-10-26T22:10:00.163","status":"Analyzed","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.","cvss_v4":{"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","score":9.1},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","score":9.1},"cwes":["CWE-436"],"references":["https://cna.openjsf.org/security-advisories.html","https://github.com/fastify/fastify-express/security/advisories/GHSA-6hw5-45gm-fj88","https://github.com/fastify/fastify-express/security/advisories/GHSA-6hw5-45gm-fj88"],"products":["fastify:fastify\\/express"],"source":"nvd","synced_at":"2026-10-26T22:26:44.656832877+00:00"},"epss":{"cve":"CVE-2026-33808","score":0.00483,"percentile":0.41376,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-6hw5-45gm-fj88","url":"https://osv.dev/vulnerability/GHSA-6hw5-45gm-fj88","summary":"@fastify/express has a middleware authentication bypass via URL normalization gaps (duplicate slashes and semicolons)","modified":"2026-09-10T03:50:43.432371441Z","packages":[{"ecosystem":"npm","name":"@fastify/express","purl":"pkg:npm/%40fastify/express","ranges":["<4.0.5"],"fixed":["4.0.5"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}