Input validation error in envoy - CVE-2026-47778
Published: June 24, 2026
Vulnerability identifier: #VU135106
CSH Severity: Low
CVSS v4: 5.9 [CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-47778
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to bypass host authentication.
The vulnerability exists due to improper input validation in DefaultCertValidator::verifySubjectAltName when validating DNS subject alternative names in upstream TLS certificates. A remote privileged user can present a certificate containing a dNSName SAN with an embedded NUL byte to bypass host authentication.
Only DNS SAN validation is affected. Exploitation requires Envoy to use auto_sni and auto_san_validation for upstream connections, and depends on a trusted certificate authority accepting certificates with embedded NUL characters.
Affected software
envoy
How to mitigate CVE-2026-47778
Install security update from vendor's website.
envoy - addressed in versions 1.35.12, 1.36.8, 1.37.4, 1.38.2