CVE-2026-25086: WebCTRL Auth Bypass Vulnerability

CVE-2026-25086 Overview

CVE-2026-25086 affects Automated Logic WebCTRL, a building automation system used in industrial control system (ICS) environments. The vulnerability stems from improper restriction on port binding [CWE-605], allowing a local attacker to bind to the same network port used by the WebCTRL service. Once bound, the attacker can craft and send malicious packets while impersonating the legitimate WebCTRL service without injecting code into the application. CISA published an advisory for this issue as ICSA-26-078-08.

Critical Impact
A local attacker can impersonate the WebCTRL service, intercepting or manipulating building automation traffic without modifying the WebCTRL software itself.

Affected Products

Automated Logic WebCTRL (see vendor advisory for affected versions)
Building automation deployments referenced in CISA ICS Advisory ICSA-26-078-08
Operational Technology (OT) environments running WebCTRL services

Discovery Timeline

2026-03-21 - CVE-2026-25086 published to the National Vulnerability Database
2026-03-23 - Last updated in NVD database

Technical Details for CVE-2026-25086

Vulnerability Analysis

The vulnerability is classified under [CWE-605] (Multiple Binds to the Same Port). WebCTRL listens on a specific network port to handle building automation traffic. The operating system or application logic does not enforce exclusive ownership of that port under all conditions. An attacker with local access can bind a rogue process to the same port before or alongside the legitimate service.

Once bound, the attacker controls how incoming packets are processed. The rogue listener can respond to clients as if it were the WebCTRL service. This enables packet crafting, response forgery, and traffic redirection without requiring code injection into WebCTRL itself.

The attack vector is local, meaning the attacker must already have access to the host running WebCTRL or to a system sharing its network context. No authentication or user interaction is required to exploit the flaw. Successful exploitation impacts confidentiality and integrity of the data exchanged with WebCTRL clients.

Root Cause

The root cause is insufficient enforcement of exclusive port binding for the WebCTRL listener. The service does not validate sole ownership of its communication port, allowing a competing process on the same host to claim it under specific conditions.

Attack Vector

An attacker first obtains local access to the system hosting WebCTRL or to an adjacent host able to bind the same port. The attacker then starts a process that binds to the WebCTRL port. Clients connecting to WebCTRL may route requests to the rogue listener, which returns attacker-controlled responses. See the CISA ICS Advisory ICSA-26-078-08 and the GitHub CSAF Document for protocol-level details.

Detection Methods for CVE-2026-25086

Indicators of Compromise

Unexpected processes listening on the WebCTRL service port as shown by netstat -ano or ss -tlnp
WebCTRL clients receiving malformed or unsigned responses inconsistent with prior baselines
Service restart loops or bind failures recorded in WebCTRL application logs
New or unsigned executables present in user-writable directories on WebCTRL hosts

Detection Strategies

Baseline the process identifier and binary path of the WebCTRL listener, then alert on changes
Monitor for non-WebCTRL processes attempting to bind to the WebCTRL port
Correlate process creation events with subsequent socket bind operations on ICS hosts
Inspect WebCTRL client traffic for protocol anomalies indicating response forgery

Monitoring Recommendations

Forward Windows Event Logs, Sysmon socket events, and Linux audit logs from WebCTRL hosts to a centralized SIEM
Enable network traffic capture on OT segments hosting WebCTRL for retrospective analysis
Alert on any local logon to WebCTRL servers outside scheduled maintenance windows

How to Mitigate CVE-2026-25086

Immediate Actions Required

Restrict local and interactive logon to WebCTRL hosts to authorized administrators only
Apply vendor guidance referenced in the Automated Logic Security Commitment page as updates become available
Inventory all WebCTRL deployments and verify the binary path and process owner of the listener
Segment OT networks running WebCTRL from corporate and internet-accessible zones

Patch Information

Refer to the CISA ICS Advisory ICSA-26-078-08 and the Automated Logic Security Commitment page for vendor-provided patch and version guidance. Apply updates following standard ICS change-control procedures and validate WebCTRL functionality after deployment.

Workarounds

Run WebCTRL under a dedicated service account with exclusive rights to its listening port
Use host-based firewall rules to restrict which local processes and remote hosts can communicate with the WebCTRL port
Disable unused local user accounts and enforce least privilege on WebCTRL servers
Monitor port ownership continuously and alert on any rebind event

bash

# Configuration example: identify the process bound to the WebCTRL port
# Replace <PORT> with the WebCTRL listening port from your deployment

# Linux
sudo ss -tlnp | grep :<PORT>

# Windows (PowerShell)
Get-NetTCPConnection -LocalPort <PORT> | Select-Object -Property State,OwningProcess
Get-Process -Id <OwningProcess>