SB2026110354 - Path traversal in Fastify-http-proxy

CSH
CYBERSECURITY HELP
Sign In REGISTER

Main Vulnerability Database SB2026110354

SB2026110354 - Path traversal in Fastify-http-proxy

Published: November 3, 2026

Security Bulletin ID SB2026110354
CSH Severity
High
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Data manipulation

Breakdown by Severity

High 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 vulnerability.


1) Path traversal (CVE-ID: CVE-2026-120213)

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

CVSSv4: 9.3 [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]


The vulnerability allows a remote attacker to bypass upstream path restrictions and potentially access or modify protected resources in the proxied service.

The vulnerability exists due to failure to re-encode URL-decoded route parameters in the rewritePrefix handling of @fastify/http-proxy when processing requests with parameterized prefix and rewritePrefix options. A remote attacker can supply an encoded slash combined with an encoded fragment or query delimiter to inject upstream path segments and discard a mandatory suffix, potentially bypassing authorization or enabling server-side request forgery depending on the upstream service. For example, with prefix: '/tenants/:tenantId/public-avatar' and rewritePrefix: '/:tenantId/public-avatar', /tenants/admin%2fmaster-keys%23/public-avatar forwards GET /admin/master-keys, while /tenants/admin%2fusers%3ftruncate=/public-avatar forwards GET /admin/users.


Remediation

Install update from vendor's website.

References