CVE-2021-34893
📋 TL;DR
CVE-2021-34893 is a heap-based buffer overflow vulnerability in Bentley View's BMP file parser that allows remote code execution. Attackers can exploit this by tricking users into opening malicious BMP files or visiting malicious web pages. Users of affected Bentley View versions are at risk.
💻 Affected Systems
- Bentley View
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control of the affected system, potentially leading to data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Attacker executes arbitrary code in the context of the current user, potentially installing malware, stealing sensitive data, or using the system as a foothold for further attacks.
If Mitigated
If proper controls like application whitelisting and least privilege are in place, impact is limited to the user's privileges and may be contained by security controls.
🎯 Exploit Status
Exploitation requires user interaction but is technically straightforward once malicious file is opened. ZDI published advisory but no public exploit code.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.16.0.80 and later
Vendor Advisory: https://www.bentley.com/en/common-vulnerability-exposure/BE-2021-0002
Restart Required: Yes
Instructions:
1. Download latest Bentley View from official Bentley website. 2. Install the update. 3. Restart the application. 4. Verify version is 10.16.0.80 or higher.
🔧 Temporary Workarounds
Block BMP file extensions
windowsPrevent Bentley View from opening BMP files via group policy or application control
Using Group Policy: Computer Configuration > Policies > Windows Settings > Security Settings > Software Restriction Policies > Additional Rules > New Path Rule: Path: *.bmp, Security Level: Disallowed
Run with reduced privileges
windowsRun Bentley View with standard user privileges instead of administrator rights
🧯 If You Can't Patch
- Implement application whitelisting to prevent execution of unauthorized code
- Use network segmentation to isolate Bentley View systems from critical assets
🔍 How to Verify
Check if Vulnerable:
Check Bentley View version: Open Bentley View > Help > About. If version is 10.15.0.75 or earlier, system is vulnerable.Check Version:
wmic product where name="Bentley View" get versionVerify Fix Applied:
Verify version is 10.16.0.80 or higher in Help > About dialog.📡 Detection & Monitoring
Log Indicators:
- Unusual process creation from Bentley View executable
- Multiple failed BMP file parsing attempts
- Crash logs from Bentley View with memory access violations
Network Indicators:
- Outbound connections from Bentley View to unknown IPs
- DNS requests for suspicious domains after BMP file opening
SIEM Query:
source="windows" AND process_name="BentleyView.exe" AND (event_id=4688 OR event_id=1) AND parent_process_name="explorer.exe"