CVE-2021-31507
📋 TL;DR
CVE-2021-31507 is a buffer overflow vulnerability in OpenText Brava! Desktop that allows remote code execution when a user opens a malicious CGM file or visits a malicious webpage. Attackers can exploit this to run arbitrary code with the privileges of the current user. This affects users of OpenText Brava! Desktop version 16.6.3.84.
💻 Affected Systems
- OpenText Brava! Desktop
📦 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 malicious code in the context of the current user, potentially stealing sensitive documents, installing malware, or establishing persistence on the system.
If Mitigated
Limited impact if proper application sandboxing, least privilege principles, and network segmentation are implemented, potentially containing the exploit to a single user session.
🎯 Exploit Status
Exploitation requires user interaction (opening malicious file or visiting malicious page) but the vulnerability itself is straightforward to exploit once the malicious payload is delivered.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 16.6.4 or later
Vendor Advisory: https://www.opentext.com/products/brava
Restart Required: Yes
Instructions:
1. Download the latest version of OpenText Brava! Desktop from the official OpenText website. 2. Uninstall the current vulnerable version. 3. Install the updated version. 4. Restart the system to ensure all components are properly loaded.
🔧 Temporary Workarounds
Disable CGM file association
windowsRemove or modify file associations so CGM files do not automatically open with Brava! Desktop
Control Panel > Default Programs > Associate a file type or protocol with a program > Select .cgm > Change program
Block CGM files at network perimeter
allConfigure email gateways and web proxies to block or quarantine CGM files
🧯 If You Can't Patch
- Implement application whitelisting to prevent execution of unauthorized code
- Run Brava! Desktop with restricted user privileges (non-admin account)
🔍 How to Verify
Check if Vulnerable:
Check the installed version of Brava! Desktop via Control Panel > Programs and Features or by opening Brava! Desktop and checking Help > AboutCheck Version:
wmic product where name="Brava! Desktop" get versionVerify Fix Applied:
Verify the installed version is 16.6.4 or later using the same method as checking vulnerability📡 Detection & Monitoring
Log Indicators:
- Multiple failed attempts to open CGM files
- Unexpected process creation from Brava! Desktop executable
- Crash logs from Brava! Desktop with memory access violations
Network Indicators:
- Downloads of CGM files from untrusted sources
- Network connections initiated by Brava! Desktop to suspicious external IPs
SIEM Query:
process_name="brava.exe" AND (event_id=1000 OR event_id=1001) OR file_extension=".cgm" AND source_ip NOT IN trusted_networks🔗 References
- https://www.zerodayinitiative.com/advisories/ZDI-21-685/
- https://www.cvedetails.com/vulnerability-list/vendor_id-2032/product_id-96672/Opentext-Brava-Desktop.html?page=1&opec=1&order=1&trc=35&sha=37f4ed0596f8ccacca7d571f22a38c97b0f19f4c
- https://www.opentext.com/products/brava
- https://www.zerodayinitiative.com/advisories/ZDI-21-685/
