CVE-2026-82767: SGA1000 XSS Vulnerability

CVE-2026-82767 Overview

CVE-2026-82767 is a cross-site scripting (XSS) vulnerability affecting the Contec SGA1000 device. An attacker on an adjacent network can inject script content that executes in the browser of an authenticated user who interacts with the crafted input. The flaw is categorized under CWE-79: Improper Neutralization of Input During Web Page Generation. Successful exploitation requires user interaction, and the impact is limited to a subsequent system rather than the vulnerable component itself. Details are published in JVN Security Alert JVNVU99009004 and the Contec Security Information Document.

Critical Impact
An authenticated user visiting attacker-controlled content in the SGA1000 web interface may have arbitrary script executed in their browser session, enabling session abuse or interface manipulation.

Affected Products

Contec SGA1000
Refer to the Contec Security Information Document for affected firmware versions
See JVN Security Alert JVNVU99009004 for coordinated advisory details

Discovery Timeline

2026-09-14 - CVE-2026-82767 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-82767

Vulnerability Analysis

The SGA1000 web interface fails to properly neutralize user-controlled input before rendering it in web pages returned to clients. When an authenticated user loads a page containing crafted input, the browser interprets injected markup as executable script. The vulnerability requires adjacent network access and user interaction, which constrains remote mass exploitation but leaves internal network attackers a viable path. The scope crosses a trust boundary: execution occurs in the victim's browser rather than the server component, affecting confidentiality and integrity of subsequent systems the user interacts with through that session.

Root Cause

The root cause is improper neutralization of input during web page generation [CWE-79]. The SGA1000 firmware does not consistently apply output encoding or contextual escaping when reflecting or storing user-supplied data that later appears in the administrative interface. Without HTML entity encoding, JavaScript context escaping, or a restrictive Content Security Policy, attacker-controlled strings become active script when rendered.

Attack Vector

An attacker positioned on the same logical network segment as the SGA1000 delivers a payload through an input field or parameter that the web interface later renders. A logged-in administrator or operator triggers execution by loading the affected page or clicking a crafted link. The injected script runs with the privileges of the authenticated session, allowing the attacker to read session tokens accessible to script, perform actions on behalf of the user, or modify displayed content. Because the CVSS 4.0 vector records no direct impact to the vulnerable component itself, the practical impact centers on the user's browser and any downstream systems reachable through that session.

No verified proof-of-concept code is publicly available. See the JVN advisory and Contec advisory for vendor-provided technical detail.

Detection Methods for CVE-2026-82767

Indicators of Compromise

HTTP requests to the SGA1000 web interface containing <script>, javascript:, event handler attributes such as onerror= or onload=, or URL-encoded equivalents in parameters or form fields.
Web interface responses that reflect submitted input without HTML entity encoding of <, >, ", ', and &.
Unexpected outbound requests from administrator browsers to unfamiliar hosts shortly after accessing the SGA1000 management interface.

Detection Strategies

Inspect web server and reverse proxy logs for requests to SGA1000 management URLs containing script-like payloads or encoded XSS patterns.
Deploy web application firewall rules that flag reflected and stored XSS signatures targeting the device's management endpoints.
Correlate administrator authentication events with subsequent anomalous browser-originated network activity.

Monitoring Recommendations

Enable centralized logging for SGA1000 web interface access and forward logs to a SIEM for retention and query.
Monitor for repeated failed input validation errors or unusual parameter values on management endpoints.
Alert on administrator sessions that generate cross-origin requests immediately after loading device pages.

How to Mitigate CVE-2026-82767

Immediate Actions Required

Apply the firmware update published by Contec as described in the Contec Security Information Document.
Restrict access to the SGA1000 management interface to a dedicated administrative VLAN or jump host.
Require administrators to use a hardened, dedicated browser profile when managing the device and to log out immediately after use.

Patch Information

Contec has published fixed firmware and mitigation guidance in the Contec Security Information Document. The coordinated advisory is available at JVN Security Alert JVNVU99009004. Apply the vendor-supplied firmware version referenced in those advisories.

Workarounds

Place the SGA1000 management interface behind network access controls that limit reachability to authorized administrator hosts only.
Configure browsers used for device administration to disable JavaScript for the management origin where operationally feasible.
Instruct administrators not to follow untrusted links or open unexpected content while a session to the SGA1000 is active.

bash

# Configuration example: restrict SGA1000 management access to an administrative subnet
# Replace 10.10.20.0/24 with your admin subnet and 192.0.2.10 with the SGA1000 IP
iptables -A FORWARD -s 10.10.20.0/24 -d 192.0.2.10 -p tcp --dport 443 -j ACCEPT
iptables -A FORWARD -d 192.0.2.10 -p tcp --dport 443 -j DROP