CVE-2026-86105

watchguard fireware

score 0MEDIUM 6

Summary

An improper authorization vulnerability in Fireware OS's Access Portal reverse proxy allows an authenticated, low-privileged Access Portal user to access other web applications they are not authorized for by sending a specially crafted request for a different resource which they are authorized to access.

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) · Authentication bypass or missing authorisation 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

Admin or API actions with no successful login before them in the same session
New admin accounts, API keys or tokens created shortly after unusual requests
Requests to admin or API endpoints from internet IPs
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

Account and group changes · ATT&CK DS0002 User Account Creation / Modification

Sentinel: SecurityEvent (4720, 4728, 4732, 4756)AuditLogsIdentityDirectoryEvents
Splunk: Change.All_Changes (Account_Management)WinEventLog:Security (4720, 4732)
CrowdStrike: UserAccountCreatedUserAccountAddedToGroup