CVE-2022-24882: FreeRDP Authentication Bypass Vulnerability

CVE-2022-24882 Overview

CVE-2022-24882 is an authentication bypass vulnerability in FreeRDP, a free and open-source implementation of the Remote Desktop Protocol (RDP). In versions prior to 2.7.0, the NT LAN Manager (NTLM) authentication mechanism does not properly abort when a user provides an empty password value. This flaw allows attackers to bypass authentication on FreeRDP-based RDP server implementations, potentially gaining unauthorized access to systems without valid credentials.

Critical Impact

Attackers can bypass NTLM authentication on FreeRDP-based RDP servers by providing an empty password, potentially gaining unauthorized access to sensitive systems and data.

Affected Products

• FreeRDP versions prior to 2.7.0
• Fedora Extra Packages for Enterprise Linux 8.0
• Fedora 34, 35, and 36

Discovery Timeline

• April 26, 2022 - CVE-2022-24882 published to NVD
• November 3, 2025 - Last updated in NVD database

Technical Details for CVE-2022-24882

Vulnerability Analysis

This vulnerability affects FreeRDP-based RDP server implementations and represents a critical flaw in the NTLM authentication handling logic. When a user attempts to authenticate with an empty password value, the authentication process fails to properly abort and reject the connection attempt. Instead of denying access, the server-side implementation improperly handles the empty credential scenario, potentially allowing the authentication to succeed.

It is important to note that RDP clients are not affected by this vulnerability—only server-side implementations that rely on FreeRDP's NTLM authentication mechanism are at risk. This includes applications like GNOME Remote Desktop that utilize FreeRDP libraries for RDP server functionality.

Root Cause

The root cause of CVE-2022-24882 lies in improper validation within the NTLM authentication code path. When processing authentication requests, the FreeRDP server implementation fails to include a proper check for empty password values. The authentication flow continues processing an empty password as a potentially valid credential rather than immediately rejecting the authentication attempt, leading to an authentication bypass condition.

Attack Vector

The attack can be executed remotely over a network connection. An attacker targeting a vulnerable FreeRDP-based RDP server can initiate an RDP connection and provide an empty password during the NTLM authentication handshake. Due to the improper handling of this edge case, the server may accept the authentication attempt, granting the attacker unauthorized access to the system.

The attack does not require any prior privileges or user interaction, making it particularly dangerous for internet-exposed RDP servers. The vulnerability specifically impacts confidentiality by allowing unauthorized access to systems and their data.

Detection Methods for CVE-2022-24882

Indicators of Compromise

• Multiple RDP connection attempts with empty or null password values in authentication logs
• Successful RDP authentications from unexpected source IP addresses
• NTLM authentication events showing anomalous empty credential submissions
• Increased failed authentication attempts followed by unexpected successful logins

Detection Strategies

• Monitor RDP server logs for authentication attempts with empty password fields in NTLM negotiation
• Implement network-level detection rules to identify RDP connections with malformed or empty authentication credentials
• Deploy endpoint detection solutions to identify exploitation attempts against FreeRDP-based services
• Review GNOME Remote Desktop and other FreeRDP-dependent application logs for suspicious authentication patterns

Monitoring Recommendations

• Enable detailed logging for RDP server authentication events and NTLM negotiations
• Configure alerts for successful authentications that bypass normal credential validation workflows
• Monitor for connections to RDP services from unusual geographic locations or untrusted networks
• Regularly audit FreeRDP version deployments across the infrastructure to ensure patched versions are in use

How to Mitigate CVE-2022-24882

Immediate Actions Required

• Upgrade all FreeRDP installations to version 2.7.0 or later immediately
• Restrict network access to RDP servers using firewall rules until patching is complete
• Implement network-level authentication (NLA) as an additional authentication layer where possible
• Audit systems running FreeRDP-based RDP servers for signs of unauthorized access

Patch Information

The vulnerability has been patched in FreeRDP version 2.7.0. The fix was implemented through GitHub Pull Request #7750, which addresses the improper handling of empty password values in NTLM authentication. Users should upgrade to FreeRDP 2.7.0 or later, available from the official FreeRDP release page.

Distribution-specific patches are available:

• Fedora users should apply updates through the package manager for Fedora 34, 35, and 36
• Gentoo users can reference GLSA 202210-24 for patch information
• Debian users should reference the Debian LTS announcement for available updates

Workarounds

• There are currently no known workarounds for this vulnerability according to the official security advisory
• Restrict RDP server access to trusted networks only using firewall rules as a temporary measure
• Disable NTLM authentication if alternative authentication methods are available
• Consider temporarily disabling FreeRDP-based RDP server functionality until the patch can be applied

# Verify FreeRDP version and update on Fedora-based systems
rpm -q freerdp
sudo dnf update freerdp

# Verify FreeRDP version on Debian/Ubuntu systems
dpkg -l | grep freerdp
sudo apt update && sudo apt upgrade freerdp2-x11

# Restrict RDP access via firewall (temporary mitigation)
sudo firewall-cmd --remove-service=rdp --permanent
sudo firewall-cmd --reload