{"id":"CVE-2026-2880","aliases":["CLSA-2026-1784856385","EUVD-2026-9049","GHSA-8p85-9qpw-fwgw"],"status":"published","title":"@fastify/middie has an improper path normalization vulnerability","description":"A vulnerability in @fastify/middie versions \u003c 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)).\n\nWhen Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.","severity":{"version":"4.0","score":8.2,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.0043,"percentile":0.37627,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-20"],"published":"2026-02-27T18:25:37Z","modified":"2026-10-30T19:46:03Z","fixes":[{"ecosystem":"npm","package":"@fastify/middie","fixed_in":["9.2.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"@fastify/middie","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"9.2.0"}]}]},{"source":"osv","ecosystem":"TuxCare:npm","package":"@fastify/middie","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"8.3.3-tuxcare.0"},{"fixed":"8.3.3-tuxcare.2"}]}],"versions":["8.3.3","8.3.3-tuxcare.1"],"bundled":3},{"source":"osv","ecosystem":"npm","package":"@fastify/middie","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"9.2.0"}]}]}],"products":[{"vendor":"@fastify/middie","product":"@fastify/middie"},{"vendor":"fastify","product":"fastify\\/middie"}],"references":[{"url":"https://github.com/fastify/middie/security/advisories/GHSA-8p85-9qpw-fwgw","tags":["Mitigation","Vendor Advisory","advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-2880","tags":["advisory"]},{"url":"https://github.com/fastify/middie/commit/140e0dd0359d890fec7e6ea1dcc5134d6bd554d4","tags":["web"]},{"url":"https://fluidattacks.com/advisories/jimenez","tags":["web"]},{"url":"https://fluidattacks.com/advisories/policy","tags":["web"]},{"url":"https://github.com/fastify/middie/releases/tag/v9.2.0","tags":["web"]},{"url":"https://github.com/advisories/GHSA-8p85-9qpw-fwgw"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/2xxx/CVE-2026-2880.json","tags":["advisory"]},{"url":"https://github.com/fastify/middie","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-2880","title":"@fastify/middie has an improper path normalization vulnerability","description":"A vulnerability in @fastify/middie versions \u003c 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)).\n\nWhen Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.","status":"published","published":"2026-02-27T18:25:37.428Z","modified":"2026-02-27T18:56:02.979Z","cvss":[{"version":"4.0","score":8.2,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T13:48:46.911326Z"}],"euvd":[{"id":"EUVD-2026-9049","description":"A vulnerability in @fastify/middie versions \u003c 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)).\n\nWhen Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.","status":"published","published":"2026-02-27T18:25:37Z","modified":"2026-02-27T18:56:02Z","cvss":[{"version":"4.0","score":8.2,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"updated_at":"2026-11-02T19:48:13.609806Z"}],"ghsa":[{"id":"GHSA-8p85-9qpw-fwgw","title":"@fastify/middie has Improper Path Normalization when Using Path-Scoped Middleware","description":"## Summary\nA path normalization inconsistency in `@fastify/middie` can result in authentication/authorization bypass when using path-scoped middleware (for example, `app.use('/secret', auth)`).\n\nWhen Fastify router normalization options are enabled (such as `ignoreDuplicateSlashes`, `useSemicolonDelimiter`, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.\n\n## Impact\nAn unauthenticated remote attacker can access endpoints intended to be protected by middleware-based auth/authorization controls by sending specially crafted URL paths (for example, `//secret` or `/secret;foo=bar`), depending on router option configuration.\n\nThis may lead to unauthorized access to protected functionality and data exposure.\n\n## Affected versions\n- Confirmed affected: `@fastify/middie@9.1.0`\n- All versions prior to the patch are affected.\n\n## Patched versions\n- Fixed in: *9.2.0*\n\n## Details\nThe issue is caused by canonicalization drift between:\n1. `@fastify/middie` path matching for `app.use('/prefix', ...)`, and\n2. Fastify/find-my-way route lookup normalization.\n\nBecause middleware and router did not always evaluate the same normalized path, auth middleware could be skipped while route resolution still succeeded.\n\n## Workarounds\nUntil patched version is deployed:\n- Avoid relying solely on path-scoped middie guards for auth/authorization.\n- Enforce auth at route-level handlers/hooks after router normalization.\n- Disable risky normalization combinations only if operationally feasible.\n\n## Resources\n- Fluid Attacks Disclosure Policy: https://fluidattacks.com/advisories/policy\n- Fluid Attacks advisory URL: https://fluidattacks.com/advisories/jimenez\n\n## Credits\n- **Cristian Vargas** (Fluid Attacks Research Team) — discovery and report.\n- **Oscar Uribe** (Fluid Attacks) — coordination and disclosure.","status":"published","published":"2026-02-28T02:47:17Z","modified":"2026-03-07T14:41:09Z","cvss":[{"version":"4.0","score":8.2,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:39:32.329372Z"}],"nvd":[{"id":"CVE-2026-2880","description":"A vulnerability in @fastify/middie versions \u003c 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)).\n\nWhen Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.","status":"published","published":"2026-02-27T19:16:12.807Z","modified":"2026-06-17T10:31:56.523Z","cvss":[{"version":"4.0","score":8.2,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/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","level":"high","assessor":"secondary"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical","assessor":"primary"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:12:07.420927Z"}],"osv":[{"id":"CVE-2026-2880","title":"@fastify/middie has an improper path normalization vulnerability","description":"A vulnerability in @fastify/middie versions \u003c 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)).\n\nWhen Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.","status":"published","published":"2026-02-27T18:25:37.428Z","modified":"2026-10-28T02:31:08.049961552Z","cvss":[{"version":"4.0","score":8.2,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T15:45:00.530889Z"},{"id":"GHSA-8p85-9qpw-fwgw","title":"@fastify/middie has Improper Path Normalization when Using Path-Scoped Middleware","description":"## Summary\nA path normalization inconsistency in `@fastify/middie` can result in authentication/authorization bypass when using path-scoped middleware (for example, `app.use('/secret', auth)`).\n\nWhen Fastify router normalization options are enabled (such as `ignoreDuplicateSlashes`, `useSemicolonDelimiter`, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.\n\n## Impact\nAn unauthenticated remote attacker can access endpoints intended to be protected by middleware-based auth/authorization controls by sending specially crafted URL paths (for example, `//secret` or `/secret;foo=bar`), depending on router option configuration.\n\nThis may lead to unauthorized access to protected functionality and data exposure.\n\n## Affected versions\n- Confirmed affected: `@fastify/middie@9.1.0`\n- All versions prior to the patch are affected.\n\n## Patched versions\n- Fixed in: *9.2.0*\n\n## Details\nThe issue is caused by canonicalization drift between:\n1. `@fastify/middie` path matching for `app.use('/prefix', ...)`, and\n2. Fastify/find-my-way route lookup normalization.\n\nBecause middleware and router did not always evaluate the same normalized path, auth middleware could be skipped while route resolution still succeeded.\n\n## Workarounds\nUntil patched version is deployed:\n- Avoid relying solely on path-scoped middie guards for auth/authorization.\n- Enforce auth at route-level handlers/hooks after router normalization.\n- Disable risky normalization combinations only if operationally feasible.\n\n## Resources\n- Fluid Attacks Disclosure Policy: https://fluidattacks.com/advisories/policy\n- Fluid Attacks advisory URL: https://fluidattacks.com/advisories/jimenez\n\n## Credits\n- **Cristian Vargas** (Fluid Attacks Research Team) — discovery and report.\n- **Oscar Uribe** (Fluid Attacks) — coordination and disclosure.","status":"published","published":"2026-02-28T02:47:17Z","modified":"2026-02-28T06:56:21.047235Z","cvss":[{"version":"4.0","score":8.2,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T15:46:42.78452Z"},{"id":"CLSA-2026-1784856385","title":"TuxCare security update for @fastify/middie (3 CVEs)","description":"TuxCare rebuilt @fastify/middie to address 3 CVEs. Fixed in 8.3.3-tuxcare.2.","status":"published","published":"2026-08-04T14:52:48Z","modified":"2026-10-30T19:46:03.545699704Z","updated_at":"2026-11-02T15:43:46.482572Z"}]}}