CVE-2025-56535: OpenNebula v6.10.0.1 XSS Vulnerability

CVE-2025-56535 Overview

A cross-site scripting (XSS) vulnerability exists in OpenNebula v6.10.0.1 that allows attackers to execute arbitrary web scripts or HTML by injecting a crafted payload into the zone attribute parameter. This stored or reflected XSS issue can be exploited to compromise user sessions, steal credentials, or perform unauthorized actions on behalf of authenticated users within the cloud management platform.

Critical Impact
Attackers can inject malicious scripts via the zone attribute parameter, potentially leading to session hijacking, credential theft, and unauthorized access to cloud infrastructure managed by OpenNebula.

Affected Products

OpenNebula v6.10.0.1

Discovery Timeline

2026-04-29 - CVE-2025-56535 published to NVD
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2025-56535

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The flaw exists in the zone attribute parameter handling within OpenNebula's web interface. When user-supplied input is processed without proper sanitization or encoding, malicious JavaScript or HTML can be embedded and subsequently executed in the context of other users' browser sessions.

The vulnerability requires user interaction for successful exploitation, as victims must access a page containing the injected payload. However, the impact extends beyond the vulnerable origin, potentially affecting other components or users within the scope of the application's trust boundaries.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding in the zone attribute parameter processing. OpenNebula fails to properly sanitize user-controlled input before rendering it in the web interface, allowing specially crafted payloads to be interpreted as executable code rather than plain text.

Attack Vector

The attack is network-based and requires an attacker to inject a crafted XSS payload into the zone attribute parameter. This can be accomplished through various methods:

An attacker crafts a malicious URL or form submission containing JavaScript code in the zone attribute parameter
When a victim user accesses the compromised page or content, the injected script executes in their browser
The malicious script can then access session cookies, perform actions as the authenticated user, or redirect to phishing pages
Since OpenNebula manages cloud infrastructure, compromised admin sessions could lead to full infrastructure takeover

The vulnerability mechanism involves improper handling of user input in the zone attribute parameter. When this parameter is processed by OpenNebula's web interface, malicious scripts embedded within the input are executed in the victim's browser context. For detailed technical information about the exploitation technique, refer to the GitHub PoC Repository.

Detection Methods for CVE-2025-56535

Indicators of Compromise

Unusual JavaScript or HTML tags appearing in zone attribute values within OpenNebula logs
Unexpected outbound connections from user browsers to external domains after accessing OpenNebula interface
Reports of unexpected redirects or pop-ups when users interact with zone configuration pages
Anomalous session activity or privilege escalation following zone parameter modifications

Detection Strategies

Implement Web Application Firewall (WAF) rules to detect common XSS patterns in HTTP requests targeting zone parameters
Monitor application logs for suspicious input patterns containing <script>, event handlers (e.g., onerror, onload), or encoded JavaScript
Deploy browser-based Content Security Policy (CSP) violation reporting to detect attempted script injections
Use SIEM correlation rules to identify users accessing zones with suspicious attribute values

Monitoring Recommendations

Enable detailed HTTP request logging for OpenNebula web interface endpoints
Configure alerting for requests containing common XSS payloads in zone-related parameters
Monitor for CSP violation reports that may indicate XSS exploitation attempts
Track session anomalies following zone configuration page access

How to Mitigate CVE-2025-56535

Immediate Actions Required

Upgrade OpenNebula to version 7.x or the latest patched release as documented in the OpenNebula Documentation
Implement strict Content Security Policy (CSP) headers to mitigate script execution
Review and audit zone attribute configurations for any existing malicious payloads
Restrict access to zone configuration functionality to trusted administrators only

Patch Information

OpenNebula has addressed this vulnerability in newer releases. Users should consult the official OpenNebula Documentation for upgrade instructions to version 7.x, which includes security improvements. Review the GitHub PoC Repository for additional technical details about the vulnerability.

Workarounds

Implement a Web Application Firewall (WAF) with XSS filtering rules for OpenNebula endpoints
Enforce strict input validation on the zone attribute parameter at the application or reverse proxy level
Deploy Content Security Policy headers with script-src 'self' to prevent inline script execution
Limit zone configuration access to a restricted set of trusted IP addresses or VPN connections

bash

# Example CSP header configuration for Apache/Nginx
# Apache - Add to .htaccess or httpd.conf
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'"

# Nginx - Add to server block
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'";