# CVE-2026-81738: OpenVPN out-of-bounds write in tap-windows6 driver

Source: https://junglewise.ai/threats/cve-2026-81738-openvpn-out-of-bounds-write-in-tap-windows6-driver  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-07. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-81738 · Severity: info · Published 2026-09-07

OpenVPN is a widely-used VPN client used to establish secure remote connections to corporate networks and services. A flaw in the Windows tap-windows6 driver allows remote attackers to trigger an out-of-bounds memory write via specially crafted domain search configuration, potentially leading to denial of service or code execution on affected Windows systems.

Technologies: [Openvpn](https://junglewise.ai/threats/technologies/openvpn). Vendors: [Openvpn](https://junglewise.ai/threats/vendors/openvpn).

## Quick answers

**Is CVE-2026-81738 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-81738 being exploited in the wild.

**How severe is CVE-2026-81738?** Informational severity, published 7 September 2026.

**Which products and versions are affected?** Openvpn 2.5.0 through 2.7.6.

**Is there a fix for CVE-2026-81738?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-81738 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-81738?** Check whether you run Openvpn at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an out-of-bounds write condition in the tap-windows6 driver component used by OpenVPN on Windows. The flaw is triggered via crafted DOMAIN-SEARCH entries in OpenVPN configuration, allowing an attacker on the network to send specially crafted packets that exploit insufficient input validation. The attack is network-reachable and does not require prior authentication. Successful exploitation could result in denial of service (driver crash) or potentially arbitrary code execution with system privileges, depending on memory layout and exploitation technique. Versions 2.5.0 through 2.7.6 are affected; patched versions are expected from the OpenVPN project.

## Affected products

- OpenVPN OpenVPN 2.5.0 through 2.7.6

## Timeline

- 2026-09-07: disclosed

## References

- [https://community.openvpn.net/Security%20Announcements/CVE-2026-81738](https://community.openvpn.net/Security%20Announcements/CVE-2026-81738)

## Related threats

- [OpenVPN use-after-free in TLS session promotion or expiry](https://junglewise.ai/threats/cve-2026-84471-the-fix-for-was-incomplete-a-use-after-free-in-openvpn-2-6-0)
- [OpenVPN integer underflow in domain search options](https://junglewise.ai/threats/cve-2026-88964-an-integer-underflow-in-openvpn-version-2-7-alpha3-through-2-7-7)
- [OpenVPN identity impersonation via embedded NUL in certificate subject](https://junglewise.ai/threats/cve-2026-84790-openvpn-2-7-alpha1-through-2-7-7-allows-remote-authenticated)
- [OpenVPN ACK packet retransmission denial of service](https://junglewise.ai/threats/cve-2026-84732-openvpn-ack-packet-retransmission-denial-of-service)
- [OpenVPN argument parsing vulnerability on Windows](https://junglewise.ai/threats/cve-2026-84256-openvpn-argument-parsing-vulnerability-on-windows)