A newly discovered security vulnerability in OpenVPN’s Windows driver has raised alarms within the tech community. The flaw exposes systems running certain versions of OpenVPN to denial-of-service (DoS) attacks, potentially causing affected Windows machines to crash.
The vulnerability, designated as CVE-2025-50054, exists within OpenVPN’s ovpn-dco-win driver, a component responsible for handling the VPN’s data channel offload for Windows. Versions 1.3.0 and earlier of the driver, as well as OpenVPN 2.5.8 and earlier, are impacted by this flaw. When exploited, it allows local, unprivileged users to send maliciously crafted control messages that can trigger a buffer overflow in the driver. This, in turn, leads to a system crash.
While this vulnerability doesn’t expose user data, it poses a significant risk to system availability. Attackers could repeatedly crash affected systems, making them unusable until restarted or fixed.
The vulnerability arises from a heap-based buffer overflow, where malicious input sent to the vulnerable driver overflows a buffer in memory, triggering a system crash. Unlike many other vulnerabilities that may leak or compromise data, this exploit results purely in denial-of-service (DoS), disrupting the normal operation of the system.
Security experts have highlighted that this vulnerability affects systems running OpenVPN with ovpn-dco-win driver versions 1.3.0 and earlier, as well as OpenVPN 2.5.8 and earlier. In essence, this issue could crash a Windows machine whenever an attacker is able to send the crafted control message.
In response, OpenVPN has released OpenVPN 2.7_alpha2, which contains a fix for CVE-2025-50054. This release also includes a variety of improvements for Windows support. This alpha release, however, is not recommended for use in production environments.
Key changes introduced with the release include:
- Enhanced support for Windows architectures, such as WFP filters and improvements to automatic service generation.
- The new win-dco driver has become the default in OpenVPN 2.7_alpha2, replacing the older wintun driver. The new win-dco driver, part of OpenVPN’s broader effort to optimize performance, processes VPN traffic directly within the Windows kernel and eliminates the need to send data between user space and kernel space for encryption and routing.
- Fix for CVE-2025-50054 to address the buffer overflow vulnerability.
For users who rely on OpenVPN on Windows, it’ is’s crucial to take action to mitigate the risks associated with this vulnerability. Although the 2.7_alpha2 release contains the necessary fix, it isn’t yet suitable for production environments. OpenVPN is expected to release a stable version addressing this vulnerability in the coming weeks.
For Windows users, the new alpha release is available in 64-bit, ARM64, and 32-bit MSI installer formats.
Visit the OpenVPN downloads page for the latest version and release notes.
Administrators should consider restricting local access and limiting access to OpenVPN drivers until a fully stable patch is available.
Securing network components like VPN drivers is important. While this vulnerability may not specifically compromise data, its ability to cause repeated system crashes presents a risk to the health and availability of affected systems.
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