CVE-2026-42948: ELECOM Wireless AP Stored XSS Vulnerability

CVE-2026-42948 Overview

CVE-2026-42948 is a stored cross-site scripting (XSS) vulnerability affecting ELECOM wireless LAN access point devices. An authenticated administrator can inject malicious script content into the device management interface. When another administrator accesses the affected page, the stored payload executes in their browser session. The flaw is classified under CWE-79, Improper Neutralization of Input During Web Page Generation.

Critical Impact

A malicious administrator can store arbitrary JavaScript in the device's web management interface, leading to script execution in other administrators' browsers and potential session compromise or configuration tampering.

Affected Products

• ELECOM wireless LAN access point devices (specific models listed in vendor advisory)
• Refer to the Elecom Security News Release for affected model numbers
• Refer to the JVN #03037325 Advisory for the coordinated disclosure listing

Discovery Timeline

• 2026-05-13 - CVE-2026-42948 published to NVD
• 2026-05-13 - Last updated in NVD database

Technical Details for CVE-2026-42948

Vulnerability Analysis

The vulnerability resides in the web-based administration interface of ELECOM wireless LAN access point devices. The interface fails to properly neutralize user-supplied input before storing it and rendering it back to administrators. An attacker with administrative privileges can submit input containing HTML or JavaScript through one of the configuration fields. The data is persisted in device storage and subsequently rendered into the management page without encoding.

When a second administrator views the affected page, the browser parses and executes the injected script in the context of the management interface origin. The script runs with the privileges of the viewing administrator's session, enabling actions such as session token theft, forged configuration changes, or browser-side reconnaissance of the internal network.

Root Cause

The root cause is missing output encoding and insufficient input sanitization on administrator-controlled fields in the device's web UI. The application stores raw input and reflects it back inside an HTML context without applying contextual escaping. This corresponds to a classic stored XSS pattern under CWE-79.

Attack Vector

Exploitation requires high privileges, since the attacker must already hold administrative credentials on the device. The attack is network-reachable through the management interface and requires user interaction from a second administrator who must view the page containing the stored payload. The vulnerability does not directly impact the confidentiality, integrity, or availability of the vulnerable device itself, but it can affect the subsequent administrator's browser context.

A technical proof-of-concept has not been published. See the JVN #03037325 Advisory for vendor-coordinated details.

Detection Methods for CVE-2026-42948

Indicators of Compromise

• Unexpected HTML tags, <script> elements, or event handler attributes stored in device configuration fields visible through the web management interface.
• Administrator browser sessions exhibiting unexpected outbound HTTP requests to unfamiliar domains while logged into the access point UI.
• Unauthorized configuration changes on the access point with no corresponding legitimate administrative activity in audit logs.

Detection Strategies

• Inspect saved configuration values rendered in the device web UI for embedded script syntax or encoded JavaScript payloads.
• Monitor HTTP responses from the access point management interface for reflected input that bypasses HTML encoding.
• Review browser console errors or Content Security Policy violations observed by administrators when accessing the management UI.

Monitoring Recommendations

• Capture and review web traffic to access point management interfaces from administrator workstations.
• Restrict management interface access to a dedicated administrative VLAN and log all authentication events.
• Alert on configuration field changes that contain HTML control characters such as <, >, or javascript:.

How to Mitigate CVE-2026-42948

Immediate Actions Required

• Apply firmware updates from ELECOM as listed in the Elecom Security News Release.
• Restrict access to the device management interface to trusted administrative hosts only.
• Rotate administrator credentials if multiple administrators share access and stored XSS exposure is suspected.

Patch Information

ELECOM has published a security notice with affected models and remediation guidance. Refer to the Elecom Security News Release and the JVN #03037325 Advisory for firmware versions and update procedures.

Workarounds

• Limit the number of administrator accounts and avoid sharing administrative access across untrusted personnel.
• Place the management interface on an isolated network segment unreachable from general user networks.
• Use a dedicated browser profile with no saved credentials or sensitive sessions when administering the device.

# Example: restrict management interface access via upstream firewall
# Replace 192.0.2.10 with the trusted admin workstation and 10.0.0.1 with the AP management IP
iptables -A FORWARD -s 192.0.2.10 -d 10.0.0.1 -p tcp --dport 443 -j ACCEPT
iptables -A FORWARD -d 10.0.0.1 -p tcp --dport 443 -j DROP