Improper Neutralization of Null Byte or NUL Character in OpenVPN for Windows - CVE-2026-84790
Published: October 27, 2026
Vulnerability identifier: #VU157722
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-84790
CWE-ID: CWE-158
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to potentially bypass intended certificate subject validation.
The vulnerability exists due to improper handling of null bytes in OpenVPN certificate subject validation when processing certificates containing embedded null bytes. A remote attacker can present a specially crafted certificate subject to potentially cause inconsistent interpretation of its contents and bypass intended certificate subject checks.
mbedTLS builds already reject certificates containing null bytes.
Affected software
OpenVPN for Windows
How to mitigate CVE-2026-84790
Install security update from vendor's website.
OpenVPN for Windows - update to 2.7.8