# CVE-2026-78221 - Windows openvpnserv buffer overread via UTF8 IDN NRPT domains

OpenVPN 2.x on Windows allows attackers to achieve a buffer overread in `openvpnserv` because an incorrect NRPT domains size was passed on, which becomes visible when IDN domains with UTF8 encoding are involved.

OpenVPN version 2.7_alpha1 through 2.7.6 are affected. This is fixed in version 2.7.7.

CVE Record: [CVE-2026-78221](https://www.cve.org/CVERecord?id=CVE-2026-78221)

Github:
* [OpenVPN/openvpn-private-issues#162](https://github.com/OpenVPN/openvpn-private-issues/issues/162)

Release notes:
* [openvpn-2.7.7](https://community.openvpn.net/ReleaseHistory#openvpn-277-released-3-september-2026)

Reported-By: BreachX Zero Day Labs (using Typhon AI Mil v2)