CVE-2025-56534: OpenNebula XSS Vulnerability

CVE-2025-56534 Overview

A cross-site scripting (XSS) vulnerability has been identified in the custom authenticator driver of OpenNebula v6.10.0.1. This vulnerability allows attackers to execute arbitrary web scripts or HTML content via a crafted payload, potentially compromising user sessions and enabling unauthorized actions within the cloud management platform.

Critical Impact
Attackers can inject malicious scripts through the custom authenticator driver, enabling session hijacking, credential theft, and unauthorized administrative actions within the OpenNebula cloud management interface.

Affected Products

OpenNebula v6.10.0.1
OpenNebula custom authenticator driver component

Discovery Timeline

2026-04-29 - CVE-2025-56534 published to NVD
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2025-56534

Vulnerability Analysis

This cross-site scripting vulnerability exists within the custom authenticator driver component of OpenNebula. The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation). The flaw requires user interaction to exploit, as victims must be tricked into clicking a malicious link or visiting a compromised page that delivers the XSS payload.

The vulnerability allows for unauthorized script execution within the security context of the affected OpenNebula web interface. Successful exploitation can lead to theft of session tokens, unauthorized data access, and manipulation of cloud resources under the victim's privileges.

Root Cause

The root cause stems from insufficient input validation and output encoding in the custom authenticator driver. User-supplied input is not properly sanitized before being rendered in the web interface, allowing attackers to inject malicious JavaScript or HTML content that executes in the context of authenticated user sessions.

Attack Vector

The attack is network-accessible and requires no authentication to initiate, though user interaction is required for successful exploitation. An attacker can craft a malicious URL or form submission containing JavaScript payloads targeting the vulnerable authenticator driver endpoint. When a legitimate user with an active OpenNebula session interacts with the malicious content, the injected scripts execute with the user's privileges.

The vulnerability follows a reflected or stored XSS pattern where crafted payloads can be delivered through various vectors including malicious links shared via email, social engineering, or watering hole attacks targeting OpenNebula administrators.

Detection Methods for CVE-2025-56534

Indicators of Compromise

Unusual JavaScript payloads in authentication-related HTTP requests to OpenNebula
Suspicious <script> tags or event handlers in authenticator driver parameters
Unexpected outbound connections from client browsers after interacting with OpenNebula authentication endpoints
Session tokens or credentials appearing in external request logs

Detection Strategies

Implement Web Application Firewall (WAF) rules to detect common XSS payloads in requests to the custom authenticator driver
Monitor HTTP request logs for encoded JavaScript patterns (e.g., %3Cscript%3E, javascript:, onerror=, onload=)
Deploy browser-based XSS protection headers and Content Security Policy (CSP) to detect policy violations
Review authentication logs for anomalous session behavior following suspicious requests

Monitoring Recommendations

Enable verbose logging on the OpenNebula authentication subsystem
Configure alerts for requests containing HTML special characters in authenticator parameters
Monitor for unusual administrative actions performed immediately following authentication events
Implement session anomaly detection to identify potential session hijacking attempts

How to Mitigate CVE-2025-56534

Immediate Actions Required

Upgrade to OpenNebula 7.x or later, which addresses this vulnerability according to the OpenNebula Documentation
Implement Content Security Policy (CSP) headers to restrict inline script execution
Apply input validation and output encoding on all user-controllable input processed by the custom authenticator driver
Review and restrict access to the OpenNebula administrative interface to trusted networks

Patch Information

Users are advised to upgrade to a patched version of OpenNebula. The OpenNebula 7 release documentation provides information on the latest available versions. Organizations should consult the official OpenNebula security advisories and the GitHub PoC Repository for additional technical details regarding this vulnerability.

Workarounds

Implement a reverse proxy with XSS filtering capabilities in front of the OpenNebula web interface
Deploy strict Content Security Policy headers to prevent inline script execution:
- Set Content-Security-Policy: default-src 'self'; script-src 'self'
Disable or restrict access to the custom authenticator driver if not required for operations
Educate administrators about phishing and social engineering attacks that may deliver XSS payloads

bash

# Example Content Security Policy configuration for Apache
# Add to OpenNebula virtual host configuration
Header always set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self'"
Header always set X-Content-Type-Options "nosniff"
Header always set X-XSS-Protection "1; mode=block"