An out‑of‑bounds write in the networkd process of WatchGuard Fireware OS (CWE‑787) allows an authenticated privileged user to execute arbitrary code by sending specially crafted requests to the Management Web UI. The flaw corrupts memory within the networkd service, enabling the attacker to gain the service’s privileges and potentially seize full control over the device’s network functions.

The flaw affects all WatchGuard Fireware OS releases; patching is available in Fireware OS 2026.2.1, 12.12.1, and 12.5.19.

The CVSS score of 8.6 indicates significant risk. Exploitation requires an authenticated privileged user on the Management Web UI, who can send specially crafted requests to that interface, and network reachability to the UI. The vulnerability is not listed in CISA KEV. The EPSS score of less than 1 % indicates a low probability of widespread exploitation at present. The likely attack vector is network‑based; it relies on an attacker having privileged credentials or gaining them through compromise of a legitimate user session.