CVE-2019-5619
📋 TL;DR
CVE-2019-5619 is a critical stack-based buffer overflow vulnerability in AASync FTP server software that allows remote attackers to execute arbitrary code on affected systems. Attackers can exploit this vulnerability by sending specially crafted FTP LIST commands to vulnerable servers. Organizations running AASync version 2.2.1.0 are affected.
💻 Affected Systems
- AASync FTP Server
📦 What is this software?
Aasync by Aasync
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with remote code execution leading to full administrative control, data theft, and potential lateral movement within the network.
Likely Case
Remote code execution leading to malware deployment, data exfiltration, or ransomware installation on vulnerable servers.
If Mitigated
Denial of service or application crash if exploit attempts are blocked by security controls.
🎯 Exploit Status
Metasploit module available (exploit/windows/ftp/aasync_list_reply). Exploitation is straightforward and reliable.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
No official patch available. Consider upgrading to a different FTP server solution or implementing workarounds.
🔧 Temporary Workarounds
Network-based blocking
windowsBlock FTP LIST command at network perimeter or using host-based firewall rules
netsh advfirewall firewall add rule name="Block FTP LIST" dir=in action=block protocol=TCP localport=21 remoteip=any program="%ProgramFiles%\AASync\aasync.exe"
Disable FTP service
windowsStop and disable the AASync FTP service if not required
sc stop AASync
sc config AASync start= disabled
🧯 If You Can't Patch
- Isolate vulnerable systems in a separate network segment with strict access controls
- Implement application whitelisting to prevent execution of unauthorized code
🔍 How to Verify
Check if Vulnerable:
Check AASync version in Help > About menu or examine file properties of aasync.exe. Version 2.2.1.0 is vulnerable.Check Version:
wmic datafile where name="C:\\Program Files\\AASync\\aasync.exe" get versionVerify Fix Applied:
Verify AASync is no longer running or has been upgraded to a different version. Test with Metasploit module to confirm exploit no longer works.📡 Detection & Monitoring
Log Indicators:
- Multiple failed FTP LIST commands
- Unusual FTP command patterns
- Application crash logs from AASync
Network Indicators:
- FTP LIST commands with unusually long parameters
- Traffic patterns matching Metasploit exploit module
SIEM Query:
source="ftp.log" AND command="LIST" AND (parameter_length>100 OR parameter contains "\x90")