Fire Ant Exploit on VMware ESXi & vCenter: A Blue Team Field Guide

Overview

Fire Ant is an advanced cyber-espionage campaign targeting VMware vSphere environments (vCenter, ESXi) and adjacent appliances (e.g., F5 BIG-IP). This campaign abuses a combination of known vulnerabilities, sophisticated tradecraft, and infrastructure misconfigurations to gain persistence, evade detection, and achieve lateral movement across segmented networks.

This guide is crafted for Blue Teams to understand, detect, and simulate Fire Ant’s TTPs (Tactics, Techniques, Procedures) safely in their environments.

Affected Versions

VMware vCenter

• Affected Versions:
  • vCenter Server 6.7.x (all builds prior to EOL)
  • vCenter Server 7.0 (prior to 7.0 U3o)
  • vCenter Server 8.0 (prior to 8.0 U1d)
• Fixed Versions:
  • vCenter Server 7.0 U3o
  • vCenter Server 8.0 U1d / U2+

VMware ESXi

• Affected Versions:
  • ESXi 6.7.x (prior to EOL)
  • ESXi 7.0 (prior to patches aligning with vCenter 7.0 U3o)
  • ESXi 8.0 (prior to patches aligning with vCenter 8.0 U1d/U2)

VMware Tools

• Affected Versions:
  • VMware Tools versions prior to 12.2.5
  • Linux Open VM Tools prior to 10.3.26
• Fixed Versions:
  • VMware Tools 12.2.6+ (Windows/Linux)
  • Open VM Tools 10.3.26+ (Linux)

F5 BIG-IP

• Affected Versions:
  • BIG-IP 13.x (all builds)
  • BIG-IP 14.x (all builds)
  • BIG-IP 15.x (prior to 15.1.5.1)
  • BIG-IP 16.x (prior to 16.1.2.2)
  • BIG-IP 17.x (prior to 17.0.0.1)
• Fixed Versions:
  • As per F5 K23605346 advisory

Attack Chain Summary

1. Initial Access: Exploit vCenter RCE (CVE-2023-34048) via DCERPC vulnerability.
2. ESXi Takeover: Abuse vCenter service accounts (vpxuser) to gain root-equivalent access to ESXi.
3. Persistence & Anti-Forensics: Deploy stealthy backdoors, tamper with logging (e.g., stopping vmsyslogd), and leverage unregistered VMs.
4. Host-to-Guest Execution: Exploit VMware Tools Auth Bypass (CVE-2023-20867) to execute inside guest VMs.
5. Segmentation Bypass & C2: Exploit F5 BIG-IP (CVE-2022-1388), deploy Neo-reGeorg webshells/tunnels, and abuse IPv6 paths for lateral movement.

Blue Team Testing Framework

1. Patch Compliance Verification

vCenter

# SSH into vCenter Appliance (VCSA)
vCenter_version=$(vmon-cli -V)
echo "vCenter Version: $vCenter_version"

Ensure you are on:

• vCenter 7.0 U3o or higher
• vCenter 8.0 U1d or higher

VMware Tools Inventory (PowerCLI)

Get-VM | Select Name, @{N='ToolsVersion';E={$_.ExtensionData.Guest.ToolsVersion}}, @{N='ToolsStatus';E={$_.ExtensionData.Guest.ToolsVersionStatus}} | Sort-Object ToolsStatus

Ensure Tools are updated to:

• 12.2.6+ for Windows/Linux
• 10.3.26 for older Linux VMs

F5 BIG-IP

# Check BIG-IP version
tmsh show sys version

Ensure patches are applied for CVE-2022-1388 and that iControl REST API is not exposed externally.

2. ESXi Host Forensic Checks

SSH into ESXi hosts (via trusted jump host):

Check if syslog daemon is running

ps -c | grep vmsyslogd || echo "ALERT: vmsyslogd not running"

Validate Remote Syslog Configuration

esxcli system syslog config get

Ensure logs are forwarded to a remote collector.

Hunt for Suspicious Daemons & Backdoors

ps -c | egrep -i 'python|v2ray|regeorg|autobackup|backdoor' || echo "No suspicious processes found"

Identify Unregistered VMs (Shadow VMs)

find /vmfs/volumes -maxdepth 3 -type f -name '*.vmx' > /tmp/all_vmx.txt
vim-cmd vmsvc/getallvms | awk 'NR>1 {print $NF}' > /tmp/registered_vmx.txt
comm -23 <(sort /tmp/all_vmx.txt) <(sort /tmp/registered_vmx.txt) || echo "No unregistered VMs found"

3. vCenter Forensic Checks

Review vCenter Authentication Logs

less /var/log/vmware/sso/ssoAdminServer.log
less /var/log/vmware/vpxd/vpxd.log

Indicators:

• Unusual login IPs
• Sudden session token surges
• Service restarts without admin actions

Rotate vCenter-ESXi Trust

For each ESXi host in vCenter:

Disconnect-VMHost -VMHost <hostname> -Confirm:$false
Connect-VMHost -VMHost <hostname> -User root -Password <new_password>

This regenerates vpxuser credentials per host.

4. Network Appliance & C2 Detection

Hunt for Neo-reGeorg Webshells

• Deploy YARA/Sigma rules against web server directories.
• Look for files like tunnel.aspx, shell.php with suspicious content.

F5 BIG-IP iControl REST Abuse Check

less /var/log/restjavad.0.log

Look for anomalous POST requests to admin endpoints.

IPv6 Segmentation Test

From a dual-stack VM:

ping6 <isolated-segment-ipv6-address>

Ensure IPv6 filtering mirrors IPv4 rules.

5. Guest VM Command Execution Validation

Test if host-to-guest operations require guest credentials:

Invoke-VMScript -VM "TestVM" -ScriptText "whoami" -GuestUser "invaliduser" -GuestPassword "invalidpass"

Expected:

• Patched Tools VM: Fails authentication
• Outdated Tools VM: If it succeeds, it’s vulnerable (patch immediately)

Remediation Steps

Immediate Actions

1. Patch vCenter, ESXi, VMware Tools, and F5 BIG-IP.
2. Rotate ESXi root and vpxuser credentials.
3. Enable ESXi Lockdown Mode.
4. Ensure remote syslog is configured for vCenter & ESXi.
5. Isolate management VLANs; enforce MFA for admin access.

Within 30 Days

• Harden guest API interactions (disable unnecessary features).
• Mirror IPv4 security controls on IPv6 or disable IPv6 if unsupported.
• Implement web-shell and C2 traffic detection across appliances.

Long-term Hardening

• Treat vSphere as Tier-0 infrastructure; apply privileged identity management.
• Implement infrastructure-aware telemetry beyond EDR.
• Conduct tabletop exercises for hypervisor-level incidents.

Safe Simulation Drills

Drill A — VMware Tools Exploitation Simulation

1. Set up a lab VM with outdated Tools.
2. Run Invoke-VMScript with invalid guest credentials.
3. If the script succeeds, you’ve simulated the CVE-2023-20867 scenario.
4. Patch Tools and confirm the exploit path is closed.

Drill B — IPv6 Segmentation Bypass

1. From a lab VM, attempt to reach a restricted network via IPv6.
2. If reachable, update firewall rules to enforce IPv6 parity.

Drill C — Webshell Detection

1. Stage a benign Neo-reGeorg template in a quarantined environment.
2. Validate SIEM/IDS alerts trigger on webshell patterns.

Conclusion

Fire Ant is not just a VMware bug; it’s an exploitation strategy chaining trusted components and overlooked gaps. Blue Teams must prioritize hypervisor-level visibility, patch management, and defense-in-depth around virtualization control planes.

Focus on:

• Closing known vulnerabilities (patch hygiene).
• Fortifying segmentation.
• Detecting stealthy persistence methods.

Remember: vCenter & ESXi are Tier-0 assets. Attackers treat them as such. So should defenders.

References

• Sygnia Fire Ant Report
• Broadcom VMware Advisory CVE-2023-34048
• Mandiant UNC3886 TTPs
• F5 CVE-2022-1388 Advisory
• Neo-reGeorg Project

This guide is designed for Blue Teams to safely audit, simulate, and reinforce their VMware environments without weaponizing vulnerabilities.