Is CVE-2026-33808 in the CISA KEV catalog?

No. CVE-2026-33808 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-33808?

CVE-2026-33808 has a CVSS v3 base score of 9.1 (CRITICAL).

What is the EPSS score for CVE-2026-33808?

CVE-2026-33808 has an EPSS score of 0.48% (38th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2026-33808

CRITICAL

9.1

CVSS v3

NVD

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. PatchesUpgrade to @fastify/express v4.0.5 or later.

CWE-436

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Exploit Intelligence

0.48%probability of exploitation in 30 days

38thpercentile

Low risk: more likely to be exploited than 38% of all known CVEs.

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-01.