SB20260414105 - Use of Less Trusted Source in Fastify

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Main Vulnerability Database SB20260414105

SB20260414105 - Use of Less Trusted Source in Fastify

Published: April 14, 2026

Security Bulletin ID SB20260414105
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Adjecent network
Highest impact Information disclosure

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 vulnerability.


1) Use of Less Trusted Source (CVE-ID: CVE-2026-3635)

CWE-ID: CWE-348 - Use of Less Trusted Source

CVSSv4: CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green


The vulnerability allows a remote attacker to spoof the protocol and host seen by the application.

The vulnerability exists due to use of a less trusted source in request.protocol and request.host getters when processing X-Forwarded-Proto and X-Forwarded-Host headers from direct untrusted connections. A remote attacker can send specially crafted X-Forwarded-Proto and X-Forwarded-Host headers to spoof the protocol and host seen by the application.

The issue only manifests when trustProxy is configured with a restrictive trust function, such as a specific IP, a subnet, a hop count, or a custom function.


Remediation

Install update from vendor's website.

References