by Kastro
Paper/Archive/CVE-2026-2880

CVE-2026-2880

@fastify/middie @fastify/middie — @fastify/middie has an improper path normalization vulnerability

EPSS 0.4%CVSS 9.1
critical.is priorityof 100
35
CVSS 9.1 (NVD)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 37.2.372 × 207.4No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

A vulnerability in @fastify/middie versions < 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)). When Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.

Affected

ProductAffectedFixed inSource
@fastify/middie0.0.0 – < 9.2.09.2.0CNA

Scores by source

NVD9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
openjs (CNA)8.2CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: partial

References

refgithub.com/fastify/middie/security/advisories/GHSA-8p85-9qpw-fwgw