A stack-based buffer overflow in Fireware OS’s VPN Network Access Enforcement process is triggered when an authenticated mobile VPN user sends a specially crafted request. The flaw can cause a denial‑of‑service condition and may allow execution of arbitrary code with the privileges of an unprivileged process, as defined by CWEs 121 and 129.

The vulnerability affects WatchGuard Fireware OS prior to the releases in which the fix was applied. Versions patched by the vendor include Fireware OS 2026.4 and Fireware OS 12.12.4; systems running earlier releases are vulnerable.

The CVSS base score of 6.1 indicates a moderate risk. The EPSS score is currently not available, and the vulnerability is not listed in the CISA KEV catalog. The attack requires an authenticated mobile VPN user, so the threat is limited to users with VPN credentials. An attacker can trigger a service crash to deny service to legitimate users or, if the code‑execution path is successfully exploited, gain unprivileged access to the host. The risk remains significant because the flaw is remote‑through‑VPN and the denial‑of‑service impact can disrupt business operations.