CVE-2026-33804

CriticalCVSS 9.1/10Last modified Jun 17, 2026

Description

@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.

Metrics

CVSS 3.1 9.1/10CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Weakness enumeration

CWE-436

Affected software

No affected versions have been published.

Timeline

Published: Apr 16, 2026
Last modified: Jun 17, 2026
NVD status: Analyzed

Related CVEs from 2026

CVE-2026-338058.6@fastify/reply-from v12.6.1 and earlier and @fastify/http-proxy v11.4.3 and earlier process the client's Connection header after the proxy h CVE-2026-338067.5Impact: Fastify applications using schema.body.content for per-content-type body validation can have validation bypassed entirely by prepen CVE-2026-338079.1@fastify/express v4.0.4 and earlier contains a path handling bug in the onRegister function that causes middleware paths to be doubled when CVE-2026-338089.1Impact@fastify/express v4.0.4 and earlier fails to normalize URLs before passing them to Express middleware when Fastify router normalizatio CVE-2026-338095.3A maliciously crafted TIFF file can cause image decoding to attempt to allocate up 4GiB of memory, causing either excessive resource consump CVE-2026-33819.8Compress::Raw::Zlib versions through 2.219 for Perl use potentially insecure versions of zlib. Compress::Raw::Zlib includes a copy of the z CVE-2026-338108.2When verifying a certificate chain containing excluded DNS constraints, these constraints are not correctly applied to wildcard DNS SANs whi CVE-2026-338117.5When using LookupCNAME with the cgo DNS resolver, a very long CNAME response can trigger a double-free of C memory and a crash.CVE-2026-338126.1Parsing a malicious font file can cause excessive memory allocation.CVE-2026-338137.5Parsing a WEBP image with an invalid, large size panics on 32-bit platforms.CVE-2026-338147.5When processing HTTP/2 SETTINGS frames, transport will enter an infinite loop of writing CONTINUATION frames if it receives a SETTINGS_MAX_F CVE-2026-338159.8Memory-safety vulnerability in github.com/jackc/pgx/v5.