CVE-2026-81738 - Windows single-byte overflow in write_dhcp_search_str() temp buffer

OpenVPN 2.x on Windows allows attackers to overflow a temporary buffer by a single byte via suitably crafted DHCP options, due to an off-by-one in the buffer guard in write_dhcp_search_str().

OpenVPN version 2.5.0 through 2.7.6 are affected. This is fixed in version 2.7.7.