CVE-2026-86134: fireware from 12.0 (inclusive), before 12.5.21 (exclusive), from 12.12 (inclusive), before 12.12.3 (exclusive), from…

Affected technology

fireware · from 12.0 (inclusive), before 12.5.21 (exclusive)
watchguard

fireware · from 12.12 (inclusive), before 12.12.3 (exclusive)
watchguard

fireware · from 2025.0 (inclusive), before 2026.2.3 (exclusive)
watchguard

fireware · from 2026.3 (inclusive), before 2026.3.2 (exclusive)
watchguard

Fireware OS · 2026.3 to before 2026.3.2, 2025.0 to before 2026.2.3, 12.0 to before 12.12.3
WatchGuard

Fireware OS · 12.0 to before 12.5.21
WatchGuard

Component: Not specified by the source

Attack conditions (Source advisory, CVSS 4.0): Network (remote) · No privileges required · No user interaction required

What an attacker can do

A remote, unauthenticated attacker can crash the management daemon by sending a specially request to the login interface, resulting in a denial of service. Source advisory’s CVSS 4.0 assessment (base score 8.7/10) rates confidentiality and integrity impact as none; availability impact as high.