CVE-2025-59896: Sync Breeze & Disk Pulse XSS Vulnerability

CVE-2025-59896 Overview

CVE-2025-59896 is a persistent authenticated Cross-Site Scripting (XSS) vulnerability affecting Sync Breeze Enterprise Server v10.4.18 and Disk Pulse Enterprise v10.4.18. The vulnerability exists due to insufficient validation of user input in the /add_command?sid= endpoint, specifically within the command_name parameter. An authenticated attacker can inject malicious scripts that execute in the context of other authenticated users' sessions, potentially leading to session hijacking and information theft.

Critical Impact

Attackers can steal session tokens and sensitive information from authenticated users by exploiting insufficient input validation in Flexense products.

Affected Products

• Sync Breeze Enterprise Server v10.4.18
• Disk Pulse Enterprise v10.4.18
• Other Flexense products may be affected

Discovery Timeline

• 2026-01-28 - CVE-2025-59896 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2025-59896

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The persistent nature of this XSS vulnerability means that malicious payloads are stored on the server and executed whenever a victim user accesses the affected page. This is particularly dangerous in enterprise environments where multiple administrators may access the same management interface.

The vulnerability requires authentication to exploit, meaning an attacker must first have valid credentials to the application. However, once exploited, the stored malicious content can affect any authenticated user who views the compromised page, making it an effective vector for privilege escalation or lateral movement within an organization.

Root Cause

The root cause of this vulnerability is improper input sanitization in the web application's command management functionality. The command_name parameter in the /add_command endpoint does not properly validate or encode user-supplied input before rendering it in the application's web interface. This allows an attacker to inject arbitrary HTML and JavaScript code that persists in the application and executes in the browser context of other users.

Attack Vector

The attack is conducted over the network and requires low privileges (authenticated access) along with user interaction (a victim must view the page containing the malicious payload). An authenticated attacker submits a crafted request to the /add_command?sid= endpoint with a malicious command_name value containing JavaScript code. When another authenticated user views the commands list or the affected page, the malicious script executes in their browser, allowing the attacker to steal session cookies, perform actions on behalf of the victim, or redirect the user to malicious sites.

The vulnerability mechanism involves the injection of script content through the command_name parameter. When the application renders the stored command data, it fails to properly encode the output, causing the browser to interpret the injected content as executable code. For detailed technical information, refer to the INCIBE Security Notice.

Detection Methods for CVE-2025-59896

Indicators of Compromise

• Unusual JavaScript code or HTML tags present in command names within the application database
• Web server logs showing requests to /add_command?sid= with encoded script content in the command_name parameter
• Reports from users about unexpected browser behavior or redirects when accessing the management interface
• Session hijacking incidents or unauthorized administrative actions

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block XSS payloads in HTTP requests to the /add_command endpoint
• Monitor web server access logs for requests containing common XSS patterns such as <script>, javascript:, onerror=, and other event handlers
• Deploy browser-based security controls that can detect and report Content Security Policy (CSP) violations
• Conduct regular security audits of stored data fields for anomalous content patterns

Monitoring Recommendations

• Enable detailed logging for all administrative actions within Sync Breeze Enterprise and Disk Pulse Enterprise
• Configure alerting for multiple failed or suspicious command creation attempts
• Implement real-time monitoring of user session activity to detect potential session hijacking
• Review application audit logs periodically for signs of injected malicious content

How to Mitigate CVE-2025-59896

Immediate Actions Required

• Audit existing command entries in the application for malicious content and remove any detected payloads
• Restrict access to the management interface to trusted IP addresses only
• Implement Content Security Policy (CSP) headers to mitigate the impact of XSS vulnerabilities
• Review user accounts and revoke access for any suspicious or unnecessary privileged users

Patch Information

Organizations should monitor the vendor's official channels and the INCIBE Security Notice for patch availability. Upgrade to a patched version of Sync Breeze Enterprise Server and Disk Pulse Enterprise as soon as one becomes available from Flexense.

Workarounds

• Implement a Web Application Firewall (WAF) with rules to filter XSS payloads targeting the vulnerable endpoint
• Restrict access to the /add_command functionality to only essential administrative users
• Enable HTTP-only and Secure flags on session cookies to reduce the impact of potential session theft
• Consider isolating the management interface on a separate network segment with strict access controls

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

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