CVE-2025-8153: NEC UNIVERGE IX XSS Vulnerability

CVE-2025-8153 Overview

CVE-2025-8153 is a Cross-Site Scripting (XSS) vulnerability affecting NEC Corporation UNIVERGE IX and UNIVERGE IX-R/IX-V routers. The flaw allows an attacker to inject arbitrary scripts that execute in the browser of an authenticated user who interacts with a crafted request. The issue is classified under CWE-79, Improper Neutralization of Input During Web Page Generation.

Exploitation requires user interaction, such as clicking a malicious link, but no authentication or privileges on the attacker side. Successful exploitation can compromise session data, administrative actions, or router configuration state accessible through the management interface.

Critical Impact
An unauthenticated attacker can execute arbitrary JavaScript in the context of an administrator's browser session, potentially leading to configuration tampering on NEC UNIVERGE IX network equipment.

Affected Products

NEC UNIVERGE IX from Ver.9.5 to Ver.10.7, Ver.10.8.21 to Ver.10.8.36, Ver.10.9.11 to Ver.10.9.24, Ver.10.10.21 to Ver.10.10.31, and Ver.10.11.6
NEC UNIVERGE IX-R Ver.1.3.16 and Ver.1.3.21
NEC UNIVERGE IX-V Ver.1.3.16 and Ver.1.3.21

Discovery Timeline

2025-09-17 - CVE-2025-8153 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-8153

Vulnerability Analysis

CVE-2025-8153 stems from improper neutralization of user-controllable input rendered by the UNIVERGE IX web management interface. The device fails to sanitize or encode input before reflecting it into HTML responses. An attacker can craft a URL or request containing JavaScript payloads that execute when a victim loads the response.

The vulnerability affects the router's administrative web UI, which is used by network engineers to configure routing, VPN, and firewall policies. Script execution in this context runs with the privileges of the authenticated user's session in the browser.

Root Cause

The root cause is missing or insufficient output encoding in web pages served by the UNIVERGE IX firmware. Input received through HTTP parameters is inserted directly into the response body without applying HTML entity encoding or context-aware sanitization. This allows <script> tags and event handlers supplied by an attacker to be parsed and executed by the victim's browser.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker crafts a malicious URL pointing to the vulnerable UNIVERGE IX management endpoint with an embedded script payload. The attacker then delivers the URL through phishing, chat, or a compromised web page.

When an administrator with an active session clicks the link, the injected script executes in the browser under the origin of the router's management interface. The script can read session cookies, submit configuration changes on behalf of the user, or exfiltrate credentials entered into the UI. See the NEC Security Notice NV25-005 for vendor-specific technical details.

Detection Methods for CVE-2025-8153

Indicators of Compromise

HTTP requests to the UNIVERGE IX management interface containing script tags, javascript: URIs, or common XSS payload strings such as onerror=, onload=, or alert(
Unexpected outbound connections from administrator workstations to attacker-controlled domains immediately after accessing the router management UI
Router configuration changes made from a browser session that do not correspond to a scheduled change request

Detection Strategies

Inspect web server and proxy logs for requests to UNIVERGE IX management URLs containing URL-encoded HTML metacharacters like %3Cscript%3E or %22onerror%3D
Deploy a web application firewall in front of the management interface with rules to identify reflected XSS patterns in query strings and POST bodies
Correlate administrator email or chat activity with subsequent router UI access to identify potential phishing-delivered exploitation attempts

Monitoring Recommendations

Log and alert on all administrative sessions to the UNIVERGE IX web UI, including source IP, user agent, and requested URIs
Monitor DNS and proxy telemetry for browser connections from administrator hosts to newly registered or low-reputation domains
Track configuration diffs on UNIVERGE IX devices and alert when changes occur outside approved change windows

How to Mitigate CVE-2025-8153

Immediate Actions Required

Restrict access to the UNIVERGE IX web management interface to a dedicated management network or jump host, blocking exposure to untrusted networks
Instruct administrators to avoid clicking links to router management URLs and to use bookmarks or direct entry instead
Log out of the management interface immediately after each administrative session to reduce the window for session-based exploitation

Patch Information

NEC has published advisory NV25-005 with remediation guidance and fixed firmware versions. Refer to the NEC Security Notice NV25-005 for the specific target versions and firmware upgrade procedures for UNIVERGE IX and UNIVERGE IX-R/IX-V devices. Apply the vendor-provided firmware update to eliminate the vulnerable code path.

Workarounds

Place the UNIVERGE IX management interface behind an ACL that only permits access from a trusted administrative subnet
Use a dedicated, hardened browser or a privileged access workstation for router administration, isolated from general web browsing and email
Enforce Content Security Policy and script-blocking browser extensions on administrator workstations that access network device UIs

bash

# Example ACL restricting UNIVERGE IX HTTP management access to an admin subnet
# Replace 192.0.2.0/24 with your management network and apply per NEC configuration syntax
ip access-list MGMT-ACL
 permit tcp 192.0.2.0/24 any eq 443
 deny   tcp any any eq 443
 permit ip any any