CVE-2026-82776 Overview
CVE-2026-82776 is a cross-site scripting (XSS) vulnerability affecting the Contec CONPROSYS PAC Series of programmable automation controllers. The flaw allows an attacker to execute arbitrary script code in the browser context of a logged-in user who interacts with a crafted request or link. The weakness maps to [CWE-79], improper neutralization of input during web page generation. Successful exploitation can compromise session data, alter the rendered interface, or pivot to further attacks against the industrial control environment served by the affected device.
Critical Impact
An attacker can execute arbitrary script in an authenticated operator's browser, enabling session abuse or UI manipulation on industrial automation controllers.
Affected Products
- Contec CONPROSYS PAC Series (see vendor advisory for affected models and firmware)
- Refer to the Contec Security Information Document for the complete list of impacted products and firmware versions
- Refer to JVN Security Advisory JVNVU96551518 for coordinated disclosure details
Discovery Timeline
- 2026-09-14 - CVE-2026-82776 published to NVD
- 2026-09-16 - Last updated in NVD database
Technical Details for CVE-2026-82776
Vulnerability Analysis
The issue is a stored or reflected cross-site scripting vulnerability in the web interface of CONPROSYS PAC Series controllers. The application fails to properly neutralize user-supplied input before rendering it in a response page. When an authenticated user loads the affected page, injected script executes with the privileges of that user in the browser context. In an industrial automation setting, the browser session commonly grants access to controller configuration, process telemetry, and operator commands, making script execution a meaningful pivot point.
Root Cause
The root cause is missing or insufficient output encoding of untrusted input on a web endpoint served by the controller. Input accepted from a network request is reflected into HTML, JavaScript, or attribute contexts without contextual escaping, allowing attacker-supplied markup to be parsed as executable script. The weakness is classified as [CWE-79].
Attack Vector
Exploitation requires user interaction. An attacker crafts a malicious URL or payload targeting the vulnerable endpoint and lures an authenticated operator into visiting it. Because the attack vector is network-based and requires no privileges on the target, any user with reachable network access to the controller and a targeted operator can attempt exploitation. No public proof-of-concept or in-the-wild exploitation has been reported. Refer to the JVN Security Advisory JVNVU96551518 for further technical background.
Detection Methods for CVE-2026-82776
Indicators of Compromise
- HTTP requests to the CONPROSYS PAC web interface containing script tags, javascript: URIs, or common XSS payload markers such as onerror=, onload=, or encoded <script> fragments.
- Unexpected outbound connections from operator workstations to attacker-controlled hosts shortly after loading controller web pages.
- Anomalous session activity on the controller, including configuration changes or requests originating from unusual referrers.
Detection Strategies
- Inspect web server or reverse proxy logs fronting CONPROSYS PAC devices for query strings and POST bodies containing HTML or JavaScript metacharacters.
- Deploy a web application firewall rule set that flags reflected XSS payloads targeting management interfaces on operational technology networks.
- Correlate operator browser telemetry with controller access logs to identify script execution triggered by controller-hosted pages.
Monitoring Recommendations
- Alert on new or modified administrative accounts and configuration exports on affected controllers.
- Monitor for outbound HTTP or WebSocket traffic from engineering workstations to non-corporate destinations.
- Track browser console errors and content security policy violations reported by operator endpoints when browsing controller pages.
How to Mitigate CVE-2026-82776
Immediate Actions Required
- Restrict network access to the CONPROSYS PAC web interface so it is reachable only from designated engineering workstations on a segmented OT network.
- Instruct operators to avoid clicking untrusted links while authenticated to controller management pages, and to log out when sessions are not in use.
- Apply the fixed firmware referenced in the Contec Security Information Document as soon as it is validated for the deployment.
Patch Information
Contec has published guidance in the Contec Security Information Document and coordinated disclosure through JVN Security Advisory JVNVU96551518. Review these advisories for the authoritative list of affected models, firmware versions, and remediation instructions.
Workarounds
- Place the controller behind a reverse proxy or firewall that enforces strict allow-lists for source addresses and blocks known XSS payload patterns.
- Use a dedicated browser profile with scripting restrictions when accessing the CONPROSYS PAC web interface.
- Enforce short session timeouts on the controller to limit the window in which a stolen session token can be reused.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
