Input validation error in Fastify-http-proxy - CVE-2026-16117
Published: July 20, 2026
Vulnerability identifier: #VU138402
CSH Severity: High
CVSS v4 BT: 8 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber]
CVE-ID: CVE-2026-16117
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass path restrictions and access unintended upstream paths.
The vulnerability exists due to improper input validation in the prefix rewriting logic of @fastify/http-proxy when handling requests with percent-encoded characters in the URL prefix. A remote attacker can send a specially crafted request to bypass path restrictions and access unintended upstream paths.
Depending on the upstream service configuration, this may also expose server-side request forgery or authorization bypass conditions in the proxied service.
Affected software
Fastify-http-proxy
How to mitigate CVE-2026-16117
Install security update from vendor's website.
Fastify-http-proxy - update to 11.6.0