Improper validation of certificate with host mismatch in LibreSSL - #VU153345
Published: October 6, 2026
Vulnerability identifier: #VU153345
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-297
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass hostname mismatch detection.
The vulnerability exists due to incomplete reporting of hostname mismatches in certificate verification callbacks when verifying a peer hostname. A remote attacker can present a certificate with a mismatched hostname to bypass hostname mismatch detection.
The issue concerns verification callbacks that always return 1.
Affected software
LibreSSL
Remediation
Install security update from vendor's website.
LibreSSL - update to 4.3.3