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CVE-2026-33808

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 Expre
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:c942f504996972fea730abad1844d5fe63ef524c2b719067ca74f7d9f47ea89a
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
0

Affected products and versions

1 source assertion
{"defaultStatus":"unaffected","packageURL":"pkg:npm/@fastify/express","product":"@fastify/express","vendor":"fastify","versions":[{"lessThan":"4.0.5","status":"affected","version":"0","versionType":"semver"},{"status":"unaffected","version":"4.0.5","versionType":"semver"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:377e739a8d39bc82f7c34e6c7030de96ceb1c7a9cbf80f62f13a4c125d127cb9 · sha256:65b3e7f923be5bbb… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion
{"metric":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":9.1,"baseSeverity":"CRITICAL","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityIm…
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:377e739a8d39bc82f7c34e6c7030de96ceb1c7a9cbf80f62f13a4c125d127cb9 · sha256:65b3e7f923be5bbb… · /containers/cna/metrics/0/cvssV4_0

CWE assertions

1 source assertion
{"cweId":"CWE-436","description":"CWE-436: Interpretation Conflict","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:377e739a8d39bc82f7c34e6c7030de96ceb1c7a9cbf80f62f13a4c125d127cb9 · sha256:65b3e7f923be5bbb… · /containers/cna/problemTypes/0/descriptions/0

Source references

3 source assertions
{"url":"https://cna.openjsf.org/security-advisories.html"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:377e739a8d39bc82f7c34e6c7030de96ceb1c7a9cbf80f62f13a4c125d127cb9 · sha256:65b3e7f923be5bbb… · /containers/cna/references/1
{"url":"https://github.com/fastify/fastify-express/security/advisories/GHSA-6hw5-45gm-fj88"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:377e739a8d39bc82f7c34e6c7030de96ceb1c7a9cbf80f62f13a4c125d127cb9 · sha256:65b3e7f923be5bbb… · /containers/cna/references/0
{"tags":["exploit"],"url":"https://github.com/fastify/fastify-express/security/advisories/GHSA-6hw5-45gm-fj88"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:377e739a8d39bc82f7c34e6c7030de96ceb1c7a9cbf80f62f13a4c125d127cb9 · sha256:65b3e7f923be5bbb… · /containers/adp/0/references/0

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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