SB2026110355 - Path traversal in Fastify-http-proxy

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Main Vulnerability Database SB2026110355

SB2026110355 - Path traversal in Fastify-http-proxy

Published: November 3, 2026

Security Bulletin ID SB2026110355
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Information disclosure

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 vulnerability.


1) Path traversal (CVE-ID: CVE-2026-120214)

CWE-ID: CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CVSSv4: 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]


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.


Remediation

Install update from vendor's website.

References