Path traversal in Fastify-http-proxy - CVE-2026-120214
Published: November 3, 2026
Vulnerability identifier: #VU158831
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-120214
CWE-ID: CWE-22
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass upstream path restrictions and disclose sensitive information.
The vulnerability exists due to incomplete backslash normalization before percent-decoding in the destination validation logic of @fastify/http-proxy when processing proxied request paths. A remote attacker can send a request containing percent-encoded backslash dot-segments (%5C..%5C), such as GET /pub/%5C..%5Csecret, to pass validateDestination() and escape the rewritePrefix boundary, accessing upstream resources outside the intended path restriction.
Exploitation requires an upstream that interprets a decoded backslash as a path separator.
Affected software
Fastify-http-proxy
How to mitigate CVE-2026-120214
Install security update from vendor's website.
Fastify-http-proxy - update to 11.6.3