CVE-2025-20260
📋 TL;DR
A critical buffer overflow vulnerability in ClamAV's PDF scanning allows remote attackers to crash the antivirus service or potentially execute arbitrary code. This affects all systems running vulnerable ClamAV versions that process PDF files. The vulnerability is remotely exploitable without authentication.
💻 Affected Systems
- ClamAV
📦 What is this software?
Clamav by Clamav
Clamav by Clamav
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with ClamAV process privileges, potentially leading to full system compromise.
Likely Case
Denial of service through ClamAV process crash, disrupting file scanning and potentially affecting dependent services.
If Mitigated
Limited impact if proper network segmentation and least privilege controls are in place.
🎯 Exploit Status
Exploitation requires submitting a crafted PDF file to ClamAV's scanning interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: ClamAV 1.4.3 or 1.0.9
Vendor Advisory: https://blog.clamav.net/2025/06/clamav-143-and-109-security-patch.html
Restart Required: Yes
Instructions:
1. Backup current configuration. 2. Update ClamAV using your package manager (apt-get update && apt-get upgrade clamav for Debian/Ubuntu, yum update clamav for RHEL/CentOS). 3. Restart ClamAV service (systemctl restart clamav-daemon). 4. Verify version with clamscan --version.
🔧 Temporary Workarounds
Disable PDF scanning
allTemporarily disable PDF file scanning in ClamAV configuration
Edit clamd.conf and add: ScanPDF no
Then restart: systemctl restart clamav-daemon
Network isolation
linuxRestrict network access to ClamAV scanning services
iptables -A INPUT -p tcp --dport 3310 -j DROP (for clamd network service)
🧯 If You Can't Patch
- Implement strict network segmentation to limit access to ClamAV services
- Deploy intrusion detection/prevention systems to block malicious PDF files
🔍 How to Verify
Check if Vulnerable:
Run: clamscan --version | grep -E '1\.4\.[0-2]|1\.0\.[0-8]' - if output shows version, system is vulnerable.Check Version:
clamscan --versionVerify Fix Applied:
Run: clamscan --version | grep -E '1\.4\.3|1\.0\.9' - if output shows patched version, fix is applied.📡 Detection & Monitoring
Log Indicators:
- ClamAV process crashes or abnormal termination
- Multiple failed PDF scan attempts in ClamAV logs
Network Indicators:
- Unusual PDF file submissions to ClamAV services
- Traffic spikes to ClamAV scanning ports
SIEM Query:
source="clamav" AND (event="process_crash" OR event="scan_failed") AND file_type="pdf"