Path traversal in Fastify-http-proxy - CVE-2026-85124
Published: September 8, 2026
Vulnerability identifier: #VU147354
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-85124
CWE-ID: CWE-22
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to access restricted upstream paths.
The vulnerability exists due to improper limitation of a pathname to a restricted directory in the plain HTTP request path of @fastify/http-proxy when processing requests containing backslash dot-segments. A remote attacker can send a specially crafted request to access restricted upstream paths.
Only applications relying on prefix and rewritePrefix to isolate upstream URL space are affected.
Affected software
Fastify-http-proxy
How to mitigate CVE-2026-85124
Install security update from vendor's website.
Fastify-http-proxy - update to 11.6.2