CVE-2021-39831
📋 TL;DR
This CVE describes an out-of-bounds write vulnerability in Adobe Framemaker that allows arbitrary code execution when a user opens a malicious PDF file. It affects users of Adobe Framemaker versions 2019 Update 8 and earlier, and 2020 Release Update 2 and earlier. Exploitation requires user interaction, making it a targeted attack vector.
💻 Affected Systems
- Adobe Framemaker
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise via arbitrary code execution in the context of the current user, potentially leading to data theft, ransomware deployment, or lateral movement within a network.
Likely Case
Local privilege escalation or malware installation on the victim's machine, as exploitation requires a user to open a malicious PDF, limiting widespread automated attacks.
If Mitigated
No impact if users avoid opening untrusted PDF files or if the software is patched, as the vulnerability is not remotely exploitable without user action.
🎯 Exploit Status
Exploitation requires user interaction (opening a malicious PDF), which adds a step but does not significantly increase technical difficulty for attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Adobe Framemaker 2019 Update 9 and 2020 Release Update 3 or later
Vendor Advisory: https://helpx.adobe.com/security/products/framemaker/apsb21-74.html
Restart Required: Yes
Instructions:
1. Open Adobe Framemaker. 2. Go to Help > Check for Updates. 3. Follow prompts to install the latest update. 4. Restart the application after installation.
🔧 Temporary Workarounds
Disable PDF file opening in Framemaker
windowsPrevent Framemaker from opening PDF files to block the attack vector.
Not applicable; configure via application settings or group policy.
Use alternative PDF viewers
allOpen PDF files with a different, secure application to avoid triggering the vulnerability.
Set default PDF handler to a non-vulnerable program like Adobe Acrobat Reader.
🧯 If You Can't Patch
- Implement strict user training to avoid opening PDF files from untrusted sources.
- Apply application whitelisting to block execution of malicious code from Framemaker processes.
🔍 How to Verify
Check if Vulnerable:
Check the Adobe Framemaker version via Help > About in the application; if version is 2019 Update 8 or earlier or 2020 Release Update 2 or earlier, it is vulnerable.Check Version:
On Windows: Check registry at HKEY_LOCAL_MACHINE\SOFTWARE\Adobe\Framemaker\Version or use 'wmic product where name="Adobe Framemaker" get version' in command prompt.Verify Fix Applied:
After updating, verify the version is 2019 Update 9 or later or 2020 Release Update 3 or later in Help > About.📡 Detection & Monitoring
Log Indicators:
- Unusual process creation from Framemaker.exe, such as cmd.exe or powershell.exe, after opening a PDF file.
Network Indicators:
- Outbound connections from Framemaker.exe to unknown IP addresses, indicating potential command and control activity.
SIEM Query:
Example: Process creation where parent process is Framemaker.exe and command line contains suspicious strings like 'powershell -enc' or 'cmd /c'.