A stored cross-site scripting vulnerability in OpenWrt LuCI allows adjacent network attackers to execute malicious scripts in the browser of an administrator.

This is a stored cross-site scripting (XSS) vulnerability caused by the failure to properly encode DHCPv6 lease hostnames. An attacker on the local network can inject malicious HTML/JavaScript tags into the hostname, which will be executed in the administrator's browser when the status table is viewed.

This vulnerability carries a CVSS score of 8.8, representing a High severity risk. By exploiting this, an adjacent attacker can perform malicious actions in the context of the administrator’s session, such as stealing session cookies, redirecting the user to malicious sites, or performing unauthorized administrative actions, which could ultimately lead to full network compromise.

Immediate Action: Update the LuCI web interface to version 3.0.0 or later as indicated in the vendor advisory at https://github.com/openwrt/luci/security/advisories/GHSA-686p-p8p9-x6fh.

Proactive Monitoring: Review DHCPv6 lease tables and web access logs for any evidence of malformed hostnames or unusual administrative activity.

Compensating Controls: Restrict access to the administrative web interface by limiting the networks or specific IP addresses allowed to reach the management console.

Public Exploit Available: Unknown

Administrators should update the LuCI interface immediately to version 3.0.0 or newer to remediate this flaw. Given the ease with which adjacent attackers can inject malicious payloads, ensuring that the management interface is not exposed to untrusted clients is a critical defensive measure.