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CVE-2026-33804

@fastify/middie versions 9.3.1 and earlier are vulnerable to middleware bypass when the deprecated Fastify ignoreDuplicateSlashes option is enabled. The middleware path matching logic does not account for duplicate slash normalization performed by Fastify's router, allowing requests with duplicate slashes to bypass middleware authentication and authorization checks. This only affects applications using the deprecated ignoreDuplicateSlashes option. Upgrade to @fastify/middie 9.3.2 to fix this iss
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:88a204a6c120ea7dbe78df7cd8d83ec36b2edab1e5cdcc209108ba4e421e6100
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
0

Affected products and versions

1 source assertion
{"defaultStatus":"unaffected","packageURL":"pkg:npm/@fastify/middie","product":"@fastify/middie","vendor":"@fastify/middie","versions":[{"lessThan":"9.3.2","status":"affected","version":"0","versionType":"semver"},{"status":"unaffected","version":"9.3.2","versionType":"semver"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:6427c1fec034811108d8f17f6fd3bfd514b7fdccb0ea78743762e2c95ef1c88c · sha256:b1f5894c3aae44a2… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion
{"metric":{"baseScore":7.4,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","version":"3.1"},"metric_type":"cvssV3_1"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:6427c1fec034811108d8f17f6fd3bfd514b7fdccb0ea78743762e2c95ef1c88c · sha256:b1f5894c3aae44a2… · /containers/cna/metrics/0/cvssV3_1

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:v2:6427c1fec034811108d8f17f6fd3bfd514b7fdccb0ea78743762e2c95ef1c88c · sha256:b1f5894c3aae44a2… · /containers/cna/problemTypes/0/descriptions/0

Source references

2 source assertions
{"url":"https://cna.openjsf.org/security-advisories.html"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:6427c1fec034811108d8f17f6fd3bfd514b7fdccb0ea78743762e2c95ef1c88c · sha256:b1f5894c3aae44a2… · /containers/cna/references/1
{"url":"https://github.com/fastify/middie/security/advisories/GHSA-v9ww-2j6r-98q6"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:6427c1fec034811108d8f17f6fd3bfd514b7fdccb0ea78743762e2c95ef1c88c · sha256:b1f5894c3aae44a2… · /containers/cna/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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