CVE-2021-42726
📋 TL;DR
Adobe Bridge versions 11.1.1 and earlier contain a memory corruption vulnerability when processing malicious M4A files. This could allow attackers to execute arbitrary code with the privileges of the current user. Users who open untrusted M4A files with vulnerable Adobe Bridge installations are affected.
💻 Affected Systems
- Adobe Bridge
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via arbitrary code execution leading to data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Local privilege escalation leading to user account compromise, data exfiltration, or malware installation.
If Mitigated
Limited impact due to user account restrictions, with potential data loss but no system-wide compromise.
🎯 Exploit Status
Requires user interaction to open malicious M4A file. No public exploit code available as of knowledge cutoff.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Adobe Bridge 11.1.2 or later
Vendor Advisory: https://helpx.adobe.com/security/products/bridge/apsb21-94.html
Restart Required: Yes
Instructions:
1. Open Adobe Bridge. 2. Go to Help > Check for Updates. 3. Follow prompts to install Bridge 11.1.2 or later. 4. Restart Bridge after installation.
🔧 Temporary Workarounds
Disable M4A file association
allRemove Adobe Bridge as default handler for M4A files to prevent automatic exploitation
Windows: Control Panel > Default Programs > Set Associations > Find .m4a > Change to different program
macOS: Right-click M4A file > Get Info > Open With > Select different application > Change All
Restrict file execution
allUse application control to block execution of Adobe Bridge or restrict M4A file processing
Windows: Use AppLocker or Windows Defender Application Control rules
macOS: Use Gatekeeper or third-party application control solutions
🧯 If You Can't Patch
- Implement strict user training against opening untrusted media files
- Deploy endpoint detection and response (EDR) to monitor for suspicious Adobe Bridge processes
🔍 How to Verify
Check if Vulnerable:
Check Adobe Bridge version: Open Bridge > Help > About Adobe Bridge. If version is 11.1.1 or earlier, system is vulnerable.Check Version:
Adobe Bridge does not have command-line version check. Use GUI: Help > About Adobe Bridge.Verify Fix Applied:
Verify Adobe Bridge version is 11.1.2 or later in Help > About Adobe Bridge.📡 Detection & Monitoring
Log Indicators:
- Adobe Bridge crash logs when processing M4A files
- Unexpected Adobe Bridge process spawning child processes
- File access to suspicious M4A files
Network Indicators:
- Outbound connections from Adobe Bridge process to unknown IPs post-M4A file opening
SIEM Query:
Process:Name='Adobe Bridge' AND (EventID=1000 OR EventID=1001) AND FileExtension='.m4a'