CVE-2026-86128: WatchGuard Fireware

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

A NULL pointer dereference vulnerability in Fireware OS's NetFlow packet-processing feature allows a remote, unauthenticated attacker to cause a denial of service by sending a specially crafted IPv6 packet.

Affected products

• WatchGuard Fireware: from 12.0, before 12.5.21 (fixed in 12.5.21); from 12.12, before 12.12.3 (fixed in 12.12.3); from 2025.0, before 2026.2.3 (fixed in 2026.2.3); from 2026.3, before 2026.3.2 (fixed in 2026.3.2)

Published 2026-09-30. Last modified 2026-10-06.