CVE-2023-40857
📋 TL;DR
A buffer overflow vulnerability in VirusTotal YARA v4.3.2 allows remote attackers to execute arbitrary code via the yr_execute_cod function in the exe.c component. This affects any system running vulnerable YARA versions that processes untrusted YARA rules or files. Attackers can achieve remote code execution with the privileges of the YARA process.
💻 Affected Systems
- VirusTotal YARA
📦 What is this software?
Yara by Virustotal
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise via remote code execution leading to data theft, ransomware deployment, or complete system takeover.
Likely Case
Remote code execution allowing attackers to install malware, exfiltrate data, or pivot to other systems.
If Mitigated
Limited impact if YARA runs with minimal privileges, in isolated environments, or only processes trusted rules.
🎯 Exploit Status
The vulnerability is in a core parsing function, making exploitation straightforward. Public GitHub issues contain technical details that could facilitate exploit development.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.3.3 or later
Vendor Advisory: https://github.com/VirusTotal/yara/issues/1945
Restart Required: Yes
Instructions:
1. Check current YARA version with 'yara --version'. 2. Update to version 4.3.3 or later using your package manager or from GitHub releases. 3. Restart any services or processes using YARA.
🔧 Temporary Workarounds
Restrict YARA rule sources
allOnly allow YARA to process rules from trusted, verified sources
Run YARA with minimal privileges
linuxExecute YARA processes with limited user permissions to reduce impact
sudo -u nobody yara [options]
🧯 If You Can't Patch
- Isolate YARA processes in containers or VMs with no network access
- Implement strict input validation and sandboxing for all YARA rule processing
🔍 How to Verify
Check if Vulnerable:
Run 'yara --version' and check if output is '4.3.2'Check Version:
yara --versionVerify Fix Applied:
Run 'yara --version' and confirm version is 4.3.3 or higher📡 Detection & Monitoring
Log Indicators:
- YARA process crashes
- Unusual memory access patterns in YARA processes
- Failed YARA rule compilation attempts
Network Indicators:
- Unexpected network connections from YARA processes
- Outbound traffic from systems running YARA to suspicious destinations
SIEM Query:
process_name:yara AND (event_type:crash OR memory_usage:anomalous)