CVE-2026-33804

HIGHNVD 7.47.4—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.4 under NVD CVSS v3. EPSS exploit probability: 0.1%, top 78% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
7.4
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.4Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

@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 issue. There are no workarounds other than disabling the ignoreDuplicateSlashes option.

CVSS v3
7.4
EG Score
7.4(medium)
EG Risk
—
EPSS
19.9%
KEV
Not listed

Published

April 16, 2026

Last Modified

May 14, 2026

Advisory Details (2)

Auto-updated May 14, 2026
Patch available. Sources: github.
github Patch Available

@fastify/middie vulnerable to middleware bypass via deprecated ignoreDuplicateSlashes option · Advisory · fastify/middie · GitHub

Affected: v9.2.0.

https://github.com/fastify/middie/security/advisories/GHSA-v9ww-2j6r-98q6
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
@fastify/middie—9.3.2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 38× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:24 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-20 08:32 UTCOSV refresh
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  1. 2026-06-30 23:22 UTCEPSS rescore
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  26. 2026-06-14 23:18 UTCEPSS rescore
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  68. 2026-05-20 17:00 UTCEG score recompute
  69. 2026-05-20 11:22 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2026-33804?
CVE-2026-33804 is a high vulnerability published on April 16, 2026. @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…
When was CVE-2026-33804 disclosed?
CVE-2026-33804 was first published in the National Vulnerability Database on April 16, 2026, with the most recent update on May 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33804 actively exploited?
CVE-2026-33804 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 19.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-33804?
CVE-2026-33804 has a CVSS v3 base score of 7.4 (NVD).
How do I remediate CVE-2026-33804?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33804, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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