CVE-2026-29520: Hereta ETH-IMC408M XSS Vulnerability

CVE-2026-29520 Overview

CVE-2026-29520 is a reflected cross-site scripting (XSS) vulnerability affecting the Hereta ETH-IMC408M industrial motion controller firmware version 1.0.15 and prior. The vulnerability exists in the Network Diagnosis ping function, where the ping_ipaddr parameter fails to properly sanitize user input before reflecting it back in the HTTP response. This allows attackers to inject arbitrary JavaScript code that executes in the context of an authenticated administrator's browser session.

Critical Impact

Attackers can craft malicious links that, when clicked by authenticated administrators, execute arbitrary JavaScript in their browser sessions, potentially leading to session hijacking, credential theft, or unauthorized device configuration changes.

Affected Products

• Hereta ETH-IMC408M firmware version 1.0.15
• Hereta ETH-IMC408M firmware versions prior to 1.0.15

Discovery Timeline

• 2026-03-16 - CVE-2026-29520 published to NVD
• 2026-03-17 - Last updated in NVD database

Technical Details for CVE-2026-29520

Vulnerability Analysis

This reflected XSS vulnerability (CWE-79) affects the Network Diagnosis functionality within the Hereta ETH-IMC408M web management interface. The ping diagnostic feature accepts an IP address or hostname through the ping_ipaddr parameter without adequate input validation or output encoding. When the server processes this input and returns the results page, any malicious script embedded in the parameter is reflected directly into the HTML response and executed by the victim's browser.

The attack requires user interaction—specifically, an authenticated administrator must click a crafted malicious link. Once clicked, the injected JavaScript executes within the security context of the administrator's authenticated session with the industrial controller. This can enable attackers to steal session cookies, capture credentials, perform administrative actions on behalf of the victim, or redirect the administrator to phishing pages.

Industrial motion controllers like the ETH-IMC408M are often deployed in operational technology (OT) environments where compromised administrative access could impact physical processes and machinery.

Root Cause

The root cause of this vulnerability is improper input validation and missing output encoding in the Network Diagnosis ping function. The ping_ipaddr parameter accepts arbitrary input that is reflected back to the user without sanitization, allowing script tags and other malicious HTML/JavaScript constructs to be injected and rendered by the browser. The firmware lacks proper input validation to restrict the parameter to valid IP addresses or hostnames, and fails to apply context-appropriate output encoding when rendering user-supplied data.

Attack Vector

The attack is network-based and requires social engineering to deliver the malicious link to an authenticated administrator. An attacker would craft a URL containing JavaScript payloads in the ping_ipaddr parameter and distribute it via email, chat, or other communication channels. When an administrator with an active session clicks the link, the malicious script executes in their browser context.

The vulnerability exploits the ping diagnostic interface by embedding JavaScript code within the IP address parameter. When the page renders, the injected script executes with full access to the authenticated session, enabling actions such as session token exfiltration, DOM manipulation, or triggering administrative functions on the device.

Detection Methods for CVE-2026-29520

Indicators of Compromise

• Suspicious HTTP requests to the Network Diagnosis or ping functionality containing script tags, event handlers, or encoded JavaScript payloads in the ping_ipaddr parameter
• Web server access logs showing URLs with suspicious patterns such as <script>, javascript:, or HTML event attributes in query parameters
• Reports from users of unexpected browser behavior or redirects when accessing the device management interface

Detection Strategies

• Deploy web application firewall (WAF) rules to detect and block common XSS payload patterns in HTTP requests to the ETH-IMC408M interface
• Implement content security policy (CSP) headers on the device interface to mitigate the impact of successful XSS attacks
• Monitor network traffic for requests containing suspicious characters or encoded payloads targeting the ping diagnostic endpoint
• Enable detailed logging on the device management interface to capture and alert on malformed or suspicious input values

Monitoring Recommendations

• Review web server access logs for requests to ping or network diagnostic endpoints containing unusual or malicious-looking input values
• Set up alerts for multiple failed or malformed requests targeting administrative functions
• Correlate user session activity with unexpected administrative changes that may indicate session compromise

How to Mitigate CVE-2026-29520

Immediate Actions Required

• Limit access to the ETH-IMC408M web management interface to trusted networks only, preferably via VPN or isolated management network segments
• Educate administrators about phishing risks and the importance of not clicking untrusted links while authenticated to device interfaces
• Implement network segmentation to isolate industrial controllers from general enterprise networks
• Consider disabling the web interface if not required for operational purposes

Patch Information

As of the last NVD update on 2026-03-17, no vendor patch has been identified for this vulnerability. The Archived Hereta Website and VulnCheck Advisory for Hereta XSS provide additional context. Organizations should monitor these resources and vendor communications for updates regarding firmware fixes.

Workarounds

• Restrict access to the web management interface using firewall rules or access control lists (ACLs) to limit exposure to trusted administrative workstations only
• Deploy a reverse proxy with XSS filtering capabilities in front of the device management interface
• Use browser extensions that block JavaScript execution or implement strict content security policies
• Ensure administrators log out of the device interface when not actively in use to reduce the session hijacking window

# Example: Restrict access to management interface via iptables
# Allow only trusted admin network to access device web interface
iptables -A INPUT -p tcp --dport 80 -s 192.168.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP