SB2026072014 - Unintended Proxy or Intermediary in Fastify-reply-from

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Main Vulnerability Database SB2026072014

SB2026072014 - Unintended Proxy or Intermediary in Fastify-reply-from

Published: July 20, 2026

Security Bulletin ID SB2026072014
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) Unintended Proxy or Intermediary (CVE-ID: CVE-2026-16158)

CWE-ID: CWE-441 - Unintended Proxy or Intermediary ('Confused Deputy')

CVSSv4: 9.1 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote attacker to access and modify data across security-separated upstreams.

The vulnerability exists due to an unintended proxying behavior in the URL cache key handling in the @fastify/reply-from getUpstream() routing logic when handling requests that influence the source path or upstream selection. A remote attacker can send crafted requests that cause a URL cache key collision to access and modify data across security-separated upstreams.

Only applications that route between security-separated backends using the getUpstream() option with the default URL cache enabled are affected.


Remediation

Install update from vendor's website.

References