Off-by-one in OpenVPN Server - CVE-2026-81738
Published: September 5, 2026
Vulnerability identifier: #VU147011
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-81738
CWE-ID: CWE-193
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a single-byte buffer overflow.
The vulnerability exists due to an off-by-one error in the write_dhcp_search_str() temporary-buffer guard when processing DHCP options. A remote attacker can supply suitable DHCP options to cause a single-byte buffer overflow.
Affected software
OpenVPN Server
How to mitigate CVE-2026-81738
Install security update from vendor's website.
OpenVPN Server - update to 2.7.7