CVE-2021-34123
📋 TL;DR
CVE-2021-34123 is a critical stack buffer overflow vulnerability in atasm v1.09's aprintf() function that allows remote code execution when processing malicious files. Attackers can exploit this to gain full control of affected systems. Users of atasm v1.09 are affected.
💻 Affected Systems
- atasm
📦 What is this software?
Atasm by Atasm Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining root/administrator privileges, installing persistent backdoors, and pivoting to other systems.
Likely Case
Remote code execution leading to data theft, cryptocurrency mining, or ransomware deployment on vulnerable systems.
If Mitigated
Limited impact with proper network segmentation and least privilege, potentially only affecting the atasm process.
🎯 Exploit Status
Exploit requires crafting a malicious assembly file. The bug report includes technical details that facilitate exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 1.10 or later
Vendor Advisory: https://sourceforge.net/p/atasm/bugs/23/
Restart Required: No
Instructions:
1. Download latest atasm from SourceForge. 2. Compile and install according to documentation. 3. Replace existing atasm binary with patched version.
🔧 Temporary Workarounds
Disable atasm file processing
linuxPrevent atasm from processing untrusted files by removing execute permissions or using application control.
chmod -x /usr/bin/atasm
Input validation wrapper
allCreate wrapper script that validates input files before passing to atasm.
#!/bin/bash
# Validate file before processing
if [ -f "$1" ]; then
# Add validation logic here
atasm "$1"
fi
🧯 If You Can't Patch
- Implement strict file upload validation for any application using atasm
- Run atasm in containerized/sandboxed environment with minimal privileges
🔍 How to Verify
Check if Vulnerable:
Check atasm version: atasm --version | grep '1.09'Check Version:
atasm --versionVerify Fix Applied:
Verify version is 1.10 or later: atasm --version📡 Detection & Monitoring
Log Indicators:
- Segmentation fault or crash logs from atasm process
- Unusual child processes spawned from atasm
Network Indicators:
- Outbound connections from atasm process to unknown IPs
- Unusual file downloads preceding atasm execution
SIEM Query:
process_name="atasm" AND (event_type="crash" OR parent_process!="expected_parent")