CVE-2021-43458
📋 TL;DR
CVE-2021-43458 is an unquoted service path vulnerability in Vembu BDR 4.2.0.1 that allows local attackers to escalate privileges by placing malicious executables in service directories. Attackers can achieve arbitrary code execution with SYSTEM-level privileges. This affects systems running vulnerable versions of Vembu BDR with the affected services installed.
💻 Affected Systems
- Vembu BDR
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with SYSTEM privileges leading to complete data exfiltration, ransomware deployment, or persistent backdoor installation.
Likely Case
Local privilege escalation allowing attackers to gain administrative control over the system and potentially pivot to other network resources.
If Mitigated
Limited impact with proper access controls preventing unauthorized local access and service hardening in place.
🎯 Exploit Status
Exploit code is publicly available on Exploit-DB and GitHub. Requires local access to the system but exploitation is straightforward once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Update to Vembu BDR version 4.2.0.2 or later
Vendor Advisory: https://www.vembu.com/security-advisory/
Restart Required: Yes
Instructions:
1. Download latest Vembu BDR version from vendor website. 2. Run installer with administrative privileges. 3. Follow upgrade wizard. 4. Restart system after installation completes.
🔧 Temporary Workarounds
Apply proper service path quoting
windowsManually edit Windows service configurations to add quotes around service executable paths
sc config "ServiceName" binPath= "\"C:\Path\To\Service.exe\""
sc stop "ServiceName"
sc start "ServiceName"
Restrict write permissions to service directories
windowsRemove write permissions for non-administrative users to directories containing vulnerable service executables
icacls "C:\Program Files\Vembu\BDR\" /deny Users:(OI)(CI)W
🧯 If You Can't Patch
- Implement strict access controls to prevent unauthorized local access to affected systems
- Monitor service directories for unauthorized file creation and implement file integrity monitoring
🔍 How to Verify
Check if Vulnerable:
Check if Vembu BDR version is 4.2.0.1 and examine service paths in Windows Services (services.msc) for unquoted paths containing spacesCheck Version:
Check Vembu BDR interface or registry: HKEY_LOCAL_MACHINE\SOFTWARE\Vembu\BDR\VersionVerify Fix Applied:
Verify Vembu BDR version is 4.2.0.2 or later and confirm service paths are properly quoted in Windows Services📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing unexpected service restarts
- Security logs showing privilege escalation attempts
- Application logs showing unauthorized service modifications
Network Indicators:
- Unusual outbound connections from Vembu BDR services
- Lateral movement attempts from affected systems
SIEM Query:
EventID=4688 AND (ProcessName LIKE '%hsflowd%' OR ProcessName LIKE '%VembuBDR360Agent%' OR ProcessName LIKE '%VembuOffice365Agent%') AND NewProcessName NOT LIKE '%Vembu%'