CVE-2021-21813
📋 TL;DR
CVE-2021-21813 is a stack-buffer overflow vulnerability in the HandleFileArg function where user-controlled command-line input is copied without length validation. This allows attackers to execute arbitrary code or crash the application. Users running vulnerable versions of the affected software are at risk.
💻 Affected Systems
- Specific software not named in CVE description - likely a command-line tool or utility
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with SYSTEM/root privileges leading to complete system compromise.
Likely Case
Application crash (denial of service) or limited code execution depending on exploit sophistication.
If Mitigated
No impact if patched or proper input validation is implemented.
🎯 Exploit Status
Direct memory corruption vulnerability with public technical details available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version with proper input validation (specific version depends on software)
Vendor Advisory: https://talosintelligence.com/vulnerability_reports/TALOS-2021-1280
Restart Required: No
Instructions:
1. Identify affected software from vendor advisory
2. Update to patched version
3. Verify fix with version check
🔧 Temporary Workarounds
Input Validation Wrapper
allCreate wrapper script that validates file pattern length before passing to vulnerable binary
#!/bin/bash
if [ ${#1} -gt 255 ]; then
echo "Error: File pattern too long"
exit 1
fi
./vulnerable_binary "$1"
Restrict Binary Execution
linuxLimit execution of vulnerable binary to trusted users only
chmod 750 /path/to/vulnerable_binary
setfacl -m u:trusteduser:rx /path/to/vulnerable_binary
🧯 If You Can't Patch
- Remove or disable the vulnerable binary from production systems
- Implement strict access controls to limit who can execute the vulnerable software
🔍 How to Verify
Check if Vulnerable:
Check if software version matches vulnerable range from vendor advisoryCheck Version:
Depends on specific software - typically: ./binary --version or rpm -q packagenameVerify Fix Applied:
Test with long file pattern input (> buffer size) - should reject or handle safely📡 Detection & Monitoring
Log Indicators:
- Process crashes with segmentation fault
- Unusually long command-line arguments
- Failed execution attempts
Network Indicators:
- N/A - local exploitation
SIEM Query:
Process:Name="vulnerable_binary" AND (CommandLine:"*\"*" OR CommandLine.Length>256)