CVE-2026-86131

watchguard fireware

score 30CRITICAL 9.2

Summary

A code injection vulnerability in WatchGuard Fireware OS's BOVPN Over TLS client configuration handling allows an attacker who controls the remote VPN server to execute arbitrary commands as root on the connecting Firebox.

Published 2026-09-30 · first seen here 2026-10-10

Analysis & write-ups

No technical write-up from a research team yet. Contact Zero checks Unit 42, Google/Mandiant, Microsoft, Talos, CrowdStrike, Rapid7, watchTowr and others several times a day, plus NVD and CISA reference links.

Where it shows in your logs

Edge or network appliance (firewall, VPN, gateway) · Command or code injection (remote code execution) high confidence

Appliances usually run no EDR, so device logs, firewall flow logs and the vendor's integrity checker are often the only evidence. Get the logs off the box: attackers often wipe local logs.

What to look for

Shell metacharacters or encoded payloads in requests to the appliance's management or VPN portal
Unknown processes or files on the appliance, found with the vendor's integrity check tool
Configuration changes, new local admin accounts or new VPN users on the appliance
Admin or VPN logins from unfamiliar IPs, especially VPS or hosting providers
New outbound connections from the appliance's own IP (it should rarely start connections)
Gaps in the appliance's logs, unexpected reboots or crashes, or logs that were cleared

Data sources

Appliance system and admin logs · ATT&CK DS0015 Application Log Content

Sentinel: CommonSecurityLog (CEF from Fortinet, Palo Alto, Check Point, Cisco)Syslog
Splunk: Vendor add-ons: fortigate_event, pan:system, pan:config, cisco:asa, citrix:netscaler:syslog, f5:bigip:syslogChange.All_Changes
CrowdStrike: Falcon Next-Gen SIEM: third-party firewall / VPN connectors

Authentication and sessions · ATT&CK DS0028 Logon Session Creation / DS0002 User Account Authentication

Sentinel: SigninLogsSecurityEvent (4624, 4625, 4648)DeviceLogonEventsIdentityLogonEvents_Im_Authentication
Splunk: Authentication.Authenticationpan:globalprotectVPN sourcetypes
CrowdStrike: UserLogonUserLogonFailed2Falcon Identity Protection events

Network connections · ATT&CK DS0029 Network Connection Creation / Network Traffic Flow

Sentinel: DeviceNetworkEventsCommonSecurityLog (firewall)_Im_NetworkSession
Splunk: Network_Traffic.All_TrafficFirewall sourcetypes (pan:traffic, fortigate_traffic, cisco:asa)
CrowdStrike: NetworkConnectIP4NetworkReceiveAcceptIP4NetworkConnectIP6

Process creation · ATT&CK DS0009 Process Creation

Sentinel: DeviceProcessEventsSecurityEvent (4688)Sysmon Event ID 1_Im_ProcessCreate
Splunk: Endpoint.ProcessesXmlWinEventLog:Microsoft-Windows-Sysmon/OperationalWinEventLog:Security (4688)
CrowdStrike: ProcessRollup2SyntheticProcessRollup2