CVE-2025-66956: Asseco SEE Live Access Control Vulnerability

CVE-2025-66956 Overview

CVE-2025-66956 is an Insecure Access Control vulnerability affecting the Contact Plan, E-Mail, SMS, and Fax components in Asseco SEE Live 2.0. This critical flaw allows remote attackers to access and execute attachments via a computable URL, effectively bypassing access control mechanisms that should protect sensitive file resources.

Critical Impact

This vulnerability enables unauthorized remote access to attachments across multiple communication components, potentially exposing sensitive business communications and allowing arbitrary file execution through predictable URL patterns.

Affected Products

• Asseco SEE Live 2.0 - Contact Plan component
• Asseco SEE Live 2.0 - E-Mail component
• Asseco SEE Live 2.0 - SMS and Fax components

Discovery Timeline

• 2026-03-11 - CVE-2025-66956 published to NVD
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2025-66956

Vulnerability Analysis

This vulnerability stems from improper access control implementation (CWE-284) in Asseco SEE Live 2.0's communication components. The application fails to properly validate user authorization before granting access to file attachments. The flaw allows attackers with minimal privileges to construct URLs that directly reference attachment resources, bypassing the intended authentication and authorization checks.

The scope of this vulnerability extends beyond the vulnerable component itself, potentially allowing attackers to impact resources managed by other components within the system. Successful exploitation can lead to complete compromise of confidentiality, integrity, and availability of the affected system and its data.

Root Cause

The root cause is an Insecure Access Control weakness where the application generates predictable or computable URLs for accessing file attachments. Instead of implementing proper session-based access control or token validation, the system relies on obscurity of the URL structure to protect sensitive attachments. This design flaw allows attackers who can deduce or enumerate the URL pattern to access any attachment without proper authorization.

Attack Vector

The attack is network-based and requires only low-level privileges to execute. An attacker can exploit this vulnerability by:

1. Gaining minimal authenticated access to the Asseco SEE Live 2.0 platform
2. Analyzing the URL structure used for attachment access
3. Constructing URLs to access attachments belonging to other users or communications
4. Executing malicious attachments or exfiltrating sensitive data from accessible files

The vulnerability requires no user interaction, making it particularly dangerous for automated exploitation. Once the URL pattern is understood, attackers can systematically access and execute attachments across the Contact Plan, E-Mail, SMS, and Fax components.

Additional technical details and proof-of-concept code can be found in the GitHub CVE-2025-66956 PoC repository.

Detection Methods for CVE-2025-66956

Indicators of Compromise

• Unusual access patterns to attachment URLs from unexpected source IP addresses
• Multiple sequential requests to attachment endpoints with incrementing or patterned identifiers
• Access logs showing authenticated users retrieving attachments they did not create or receive
• Anomalous file download activity from the Contact Plan, E-Mail, SMS, or Fax components

Detection Strategies

• Implement logging and alerting for all attachment access requests, including user identity and source IP
• Monitor for high-volume requests to attachment endpoints from single sources
• Deploy web application firewalls (WAF) with rules to detect URL enumeration attacks
• Correlate attachment access events with legitimate user communication records

Monitoring Recommendations

• Enable detailed access logging for all Asseco SEE Live 2.0 communication components
• Configure SIEM rules to detect access to attachments outside normal business workflows
• Review access control audit logs regularly for unauthorized access attempts
• Implement real-time alerting for suspicious attachment retrieval patterns

How to Mitigate CVE-2025-66956

Immediate Actions Required

• Restrict network access to Asseco SEE Live 2.0 to trusted networks only
• Implement additional authentication layers for attachment access endpoints
• Review and audit recent attachment access logs for signs of exploitation
• Contact Asseco for official security guidance and patch availability

Patch Information

Organizations should monitor the Asseco Corporate Website for official security advisories and patches addressing this vulnerability. Until an official patch is available, implement the recommended workarounds to reduce exposure.

Workarounds

• Deploy a reverse proxy or WAF to enforce additional access control on attachment URLs
• Implement rate limiting on attachment access endpoints to mitigate enumeration attacks
• Restrict access to the affected components to only essential personnel
• Consider disabling attachment functionality in affected components until a patch is available

# Example: WAF rule to block suspicious attachment enumeration
# Add to your web application firewall configuration
# Block requests with sequential numeric patterns in attachment URLs
SecRule REQUEST_URI "@rx /attachment/[0-9]+$" \
    "id:100001,phase:1,deny,status:403,\
    msg:'Potential attachment enumeration attempt',\
    logdata:'%{REQUEST_URI}'"