CVE-2025-59891: Sync Breeze & Disk Pulse CSRF Vulnerability

CVE-2025-59891 Overview

CVE-2025-59891 is a Cross-Site Request Forgery (CSRF) vulnerability affecting Sync Breeze Enterprise Server v10.4.18 and Disk Pulse Enterprise v10.4.18. This vulnerability allows an authenticated user to trick another authenticated user into performing unwanted actions within the application. The flaw exists due to the absence of proper CSRF token implementation, enabling attackers to craft malicious requests that execute unauthorized operations when a victim visits a specially crafted page.

Critical Impact

Attackers can leverage this CSRF vulnerability to change user passwords or create new user accounts via the /setup_login?sid= endpoint, potentially leading to complete account takeover or unauthorized administrative access.

Affected Products

• Sync Breeze Enterprise Server v10.4.18
• Disk Pulse Enterprise v10.4.18
• Flexense Products (multiple affected)

Discovery Timeline

• 2026-01-28 - CVE-2025-59891 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2025-59891

Vulnerability Analysis

This CSRF vulnerability stems from insufficient implementation of anti-forgery mechanisms in the Flexense enterprise server products. The affected application fails to validate the origin of state-changing requests, allowing attackers to craft malicious web pages that automatically submit forged requests on behalf of authenticated users.

The vulnerability is classified under CWE-352 (Cross-Site Request Forgery), which describes a weakness where a web application does not sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted it. The network-based attack vector requires user interaction, as the victim must be lured to a malicious page while authenticated to the vulnerable application.

Root Cause

The root cause of this vulnerability is the complete absence of CSRF token validation in the affected Flexense products. Properly implemented CSRF protection requires the server to generate unique, unpredictable tokens for each user session and validate these tokens with every state-changing request. Without this protection, the application cannot distinguish between legitimate user-initiated requests and forged requests originating from malicious third-party sites.

The /setup_login?sid= endpoint processes POST requests for sensitive user management operations without verifying the request origin or requiring anti-CSRF tokens, making it trivial for attackers to forge requests that modify user credentials.

Attack Vector

The attack scenario involves an attacker crafting a malicious HTML page containing a hidden form that submits a POST request to the /setup_login?sid= endpoint. This form includes the username, password, and cpassword parameters with attacker-controlled values. When an authenticated administrator or user visits the malicious page, the form automatically submits to the vulnerable server, executing the password change or user creation operation in the context of the victim's authenticated session.

The attacker can host this malicious page on any website or deliver it via phishing emails, social media links, or compromised legitimate websites. Since the victim's browser automatically includes session cookies with the forged request, the server processes it as a legitimate authenticated action.

For technical details on the vulnerability and exploitation methods, refer to the INCIBE Security Notice.

Detection Methods for CVE-2025-59891

Indicators of Compromise

• Unexpected password changes for user accounts without user-initiated requests
• New user accounts created without administrative action
• Unusual HTTP POST requests to /setup_login?sid= endpoints from external referrers
• Web server logs showing requests with external or missing Referer headers for sensitive operations

Detection Strategies

• Monitor web server access logs for POST requests to /setup_login?sid= with suspicious or missing Referer headers
• Implement alerting for user account modifications occurring outside normal administrative workflows
• Deploy web application firewalls (WAF) to detect and block requests with external Referer headers to sensitive endpoints
• Review authentication logs for password changes that lack corresponding user activity in the application

Monitoring Recommendations

• Enable detailed logging for all user management operations including password changes and account creation
• Configure SIEM rules to correlate authentication events with unusual referrer patterns
• Implement user behavior analytics to detect anomalous account modification patterns
• Monitor for multiple failed or successful login attempts following password change events

How to Mitigate CVE-2025-59891

Immediate Actions Required

• Restrict access to the Sync Breeze Enterprise and Disk Pulse Enterprise web interfaces to trusted networks only
• Implement network-level access controls to limit who can reach the /setup_login endpoint
• Educate users about phishing risks and the importance of not clicking untrusted links while authenticated
• Consider disabling the web interface if not required for operations

Patch Information

Consult the vendor for updated versions that include CSRF token protection. Review the INCIBE Security Notice for additional guidance on affected products and remediation steps. Upgrade to patched versions as soon as they become available from Flexense.

Workarounds

• Implement a reverse proxy with CSRF protection in front of the affected applications
• Configure firewall rules to restrict web interface access to specific trusted IP addresses
• Use browser isolation or separate browser profiles when accessing the administrative interface
• Log out of the application immediately after completing administrative tasks to minimize the attack window

# Example: Restrict access to web interface using iptables
# Allow only trusted management network (example: 192.168.10.0/24)
iptables -A INPUT -p tcp --dport 80 -s 192.168.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP