CVE-2022-38336: MobaXterm Auth Bypass Vulnerability

CVE-2022-38336 Overview

An access control vulnerability exists in MobaXterm versions prior to v22.1 that allows unauthenticated attackers to establish connections to the server via SSH or SFTP protocols. This authentication bypass vulnerability (CWE-287) enables unauthorized network access to systems running vulnerable versions of the software, potentially leading to complete system compromise.

Critical Impact

Attackers can bypass authentication controls to gain unauthorized SSH/SFTP access to systems running vulnerable MobaXterm versions, potentially leading to data theft, system compromise, and lateral movement within the network.

Affected Products

• Mobatek MobaXterm versions prior to v22.1

Discovery Timeline

• 2022-12-06 - CVE-2022-38336 published to NVD
• 2025-04-24 - Last updated in NVD database

Technical Details for CVE-2022-38336

Vulnerability Analysis

This vulnerability represents a critical authentication bypass flaw in MobaXterm's SSH and SFTP server implementation. The improper access control mechanism fails to properly validate authentication credentials before allowing connections, enabling unauthenticated attackers to establish sessions to the server.

The network-based attack vector means that any attacker with network access to a vulnerable MobaXterm instance can potentially exploit this vulnerability. While the attack complexity is considered high due to specific conditions that must be met, successful exploitation requires no privileges or user interaction, making it a significant concern for organizations using affected versions.

Root Cause

The vulnerability stems from improper authentication (CWE-287) in MobaXterm's SSH/SFTP server component. The access control mechanism fails to enforce proper authentication checks before establishing connections, allowing attackers to bypass the authentication process entirely. This fundamental flaw in the authentication flow permits unauthorized access to the server without providing valid credentials.

Attack Vector

The attack is executed over the network, targeting MobaXterm's SSH or SFTP server functionality. An attacker can connect to the vulnerable server and exploit the access control flaw to gain unauthorized access without providing valid authentication credentials.

The exploitation scenario involves:

1. Identifying a target system running a vulnerable version of MobaXterm with SSH/SFTP server enabled
2. Initiating a connection to the SSH or SFTP service
3. Bypassing the authentication mechanism due to the improper access control implementation
4. Gaining unauthorized access to the system

For detailed technical information about this vulnerability, refer to the SSH MITM CVE-2022-38336 Vulnerability documentation.

Detection Methods for CVE-2022-38336

Indicators of Compromise

• Unexpected SSH or SFTP connections to MobaXterm servers from unknown or external IP addresses
• Authentication logs showing successful connections without corresponding authentication events
• Unusual file access or transfer activity via SFTP protocols
• Network traffic analysis revealing SSH/SFTP sessions from unauthorized sources

Detection Strategies

• Monitor network traffic for SSH/SFTP connections to MobaXterm servers, particularly from unexpected sources
• Implement intrusion detection rules to identify connection attempts that bypass normal authentication flows
• Review authentication logs for anomalies indicating successful access without valid credential submission
• Deploy endpoint detection solutions to monitor MobaXterm process behavior and network connections

Monitoring Recommendations

• Enable verbose logging on MobaXterm SSH/SFTP server components
• Configure network monitoring to alert on SSH/SFTP traffic to internal MobaXterm instances
• Implement network segmentation to limit exposure of MobaXterm servers
• Regularly audit connection logs for unauthorized access attempts

How to Mitigate CVE-2022-38336

Immediate Actions Required

• Upgrade MobaXterm to version v22.1 or later immediately
• Disable SSH/SFTP server functionality if not required until patching is complete
• Implement network-level access controls to restrict connections to MobaXterm servers
• Review access logs to identify any potential unauthorized access that may have occurred

Patch Information

Mobatek has addressed this vulnerability in MobaXterm version v22.1 and later releases. Organizations should upgrade to the latest available version to remediate this vulnerability. Detailed information is available in the SSH MITM vulnerability documentation.

Workarounds

• Disable SSH/SFTP server functionality in MobaXterm if not operationally required
• Implement firewall rules to restrict SSH/SFTP access to trusted IP addresses only
• Use network segmentation to isolate systems running vulnerable MobaXterm versions
• Deploy a VPN or jump host requirement for remote access to systems with MobaXterm servers

# Network-level mitigation example (firewall rules)
# Restrict SSH access to MobaXterm to specific trusted IP addresses
# Windows Firewall example
netsh advfirewall firewall add rule name="Block MobaXterm SSH" dir=in action=block protocol=tcp localport=22
netsh advfirewall firewall add rule name="Allow MobaXterm SSH Trusted" dir=in action=allow protocol=tcp localport=22 remoteip=10.0.0.0/8