Input validation error in envoy - CVE-2026-47220
Published: June 24, 2026
Vulnerability identifier: #VU135114
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-47220
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper input validation in the %REQUESTED_SERVER_NAME(X:Y)% log format handler when processing requests with a missing host-related header while host fallback options are configured. A remote attacker can send a specially crafted request to cause a denial of service.
Exploitation requires the log format to use %REQUESTED_SERVER_NAME(X:Y)% with host-related fallback options such as HOST_FIRST, SNI_FIRST, or ORIG.
Affected software
envoy
How to mitigate CVE-2026-47220
Install security update from vendor's website.
envoy - addressed in versions 1.37.4, 1.38.2