CVE-2025-41762 Overview
CVE-2025-41762 is a cryptographic vulnerability affecting MBS Solutions Universal BACnet Router firmware. An unauthenticated attacker can abuse the weak hash of the backup generated by the wwwdnload.cgi endpoint to gain unauthorized access to sensitive data, including password hashes and certificates. This vulnerability falls under CWE-328 (Reversible One-Way Hash), indicating the use of cryptographic hash functions that do not provide adequate protection for sensitive data.
Critical Impact
Unauthenticated attackers can extract sensitive credentials and certificates from backup files due to weak cryptographic hashing, potentially leading to full device compromise and unauthorized network access in building automation environments.
Affected Products
- MBS Solutions Universal BACnet Router Firmware (all versions)
- MBS Solutions UBR-01 MK II
- MBS Solutions UBR-02
- MBS Solutions UBR-LON
Discovery Timeline
- 2026-03-09 - CVE-2025-41762 published to NVD
- 2026-03-11 - Last updated in NVD database
Technical Details for CVE-2025-41762
Vulnerability Analysis
This vulnerability exists in the backup generation functionality exposed through the wwwdnload.cgi endpoint on MBS Solutions Universal BACnet Router devices. The core issue stems from the use of a weak or reversible hashing algorithm to protect sensitive data within device backup files.
When a backup is generated, the device includes critical configuration data such as user credentials (password hashes) and security certificates. Due to the weak cryptographic implementation, an attacker with local access to the backup file can reverse or crack the hashes to obtain plaintext credentials. This could allow complete administrative control over the affected BACnet router devices.
BACnet (Building Automation and Control Networks) routers are commonly deployed in industrial and commercial building automation systems, making this vulnerability particularly concerning for critical infrastructure environments where these devices manage HVAC, lighting, access control, and other building systems.
Root Cause
The root cause of CVE-2025-41762 is the implementation of a weak or reversible hash algorithm (CWE-328) in the backup file generation process. Instead of using modern, cryptographically secure hashing algorithms such as bcrypt, scrypt, or Argon2 for password storage, the firmware uses an algorithm that does not provide sufficient computational complexity to resist offline attacks.
This design flaw allows attackers to efficiently recover original plaintext values from the hashed data through techniques such as rainbow table lookups, dictionary attacks, or brute force methods.
Attack Vector
The attack requires local access to obtain a backup file from the vulnerable device. The attack chain typically involves:
Backup File Acquisition: An attacker gains access to a backup file, either through direct physical access to the device, network interception, or accessing backup files stored on network shares or management systems.
Hash Extraction: The attacker extracts the weakly hashed password data and certificates from the backup file structure.
Hash Reversal: Using offline cracking tools or precomputed rainbow tables, the attacker reverses the weak hashes to obtain plaintext credentials.
Credential Abuse: With recovered credentials, the attacker can authenticate to the BACnet router with administrative privileges, potentially compromising the entire building automation network.
The vulnerability does not require authentication to exploit once the backup file is obtained, significantly lowering the barrier for successful attacks.
Detection Methods for CVE-2025-41762
Indicators of Compromise
- Unusual access patterns to the wwwdnload.cgi endpoint on affected devices
- Unauthorized backup file generation or download activities in device logs
- Unexpected authentication attempts following backup file access
- New or modified user accounts on BACnet router devices
- Changes to device certificates or security configurations
Detection Strategies
- Monitor network traffic for requests to the wwwdnload.cgi endpoint from unauthorized sources
- Implement file integrity monitoring on any systems storing device backup files
- Review access logs for the BACnet router web interface for suspicious backup operations
- Deploy network segmentation monitoring to detect lateral movement from compromised building automation systems
Monitoring Recommendations
- Enable detailed logging on all MBS Solutions BACnet router devices and forward logs to a centralized SIEM
- Establish baseline authentication patterns and alert on anomalies
- Monitor for unauthorized access to network segments containing building automation systems
- Implement network traffic analysis to detect credential stuffing or brute force attempts against router interfaces
How to Mitigate CVE-2025-41762
Immediate Actions Required
- Review the MBS Solutions Security Advisory for vendor-specific guidance and patches
- Restrict physical and network access to affected BACnet router devices
- Audit and secure all existing backup files, considering them potentially compromised
- Rotate all credentials on affected devices and any systems using shared credentials
- Implement network segmentation to isolate building automation systems from general network access
Patch Information
MBS Solutions has released a security advisory addressing this vulnerability. Administrators should consult the MBS Solutions Security Advisory for the latest firmware updates and patching instructions. Apply all available security patches as soon as possible after testing in a non-production environment.
Workarounds
- Implement strict access controls to limit who can generate or access device backup files
- Store backup files in encrypted containers using strong encryption algorithms (AES-256)
- Implement network access control lists (ACLs) to restrict access to the device web interface
- Consider disabling the backup functionality if not operationally required until patches are applied
- Deploy additional authentication layers such as VPN requirements for accessing device management interfaces
# Example: Network ACL to restrict access to BACnet router management interface
# Adjust IP ranges according to your environment
# Allow only trusted management subnet
iptables -A INPUT -p tcp --dport 80 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 10.0.100.0/24 -j ACCEPT
# Block all other access to web interface
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
