CVE-2024-49121 Overview
CVE-2024-49121 is a Denial of Service vulnerability affecting the Windows Lightweight Directory Access Protocol (LDAP) service. This vulnerability allows remote, unauthenticated attackers to cause a denial of service condition on affected Windows systems by sending specially crafted LDAP requests. The vulnerability stems from a NULL Pointer Dereference (CWE-476) issue in the LDAP service implementation.
Critical Impact
Remote attackers can disrupt Active Directory Domain Services and authentication infrastructure across an organization without requiring authentication or user interaction.
Affected Products
- Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (versions 22H2, 23H2, 24H2)
- Microsoft Windows Server 2008 (SP2 and R2 SP1)
- Microsoft Windows Server 2012 and 2012 R2
- Microsoft Windows Server 2016, 2019, 2022
- Microsoft Windows Server 2022 23H2 and Windows Server 2025
Discovery Timeline
- 2024-12-12 - CVE-2024-49121 published to NVD
- 2025-01-14 - Last updated in NVD database
Technical Details for CVE-2024-49121
Vulnerability Analysis
This vulnerability exists within the Windows LDAP service, a critical component used for directory services including Active Directory. The flaw is classified as a NULL Pointer Dereference (CWE-476), which occurs when the LDAP service attempts to access memory through a null pointer during the processing of certain LDAP operations.
The attack can be executed remotely over the network without requiring any privileges or user interaction. When exploited, the vulnerability causes the LDAP service to crash, resulting in a denial of service condition that affects availability of directory services, user authentication, and any applications dependent on LDAP functionality.
Root Cause
The root cause of CVE-2024-49121 is a NULL Pointer Dereference condition in the Windows LDAP service. This occurs when the service fails to properly validate input before dereferencing a pointer, allowing specially crafted network requests to trigger a condition where a null pointer is accessed. This results in an unhandled exception that causes the service to terminate unexpectedly.
Attack Vector
The attack vector for this vulnerability is network-based, allowing remote exploitation without authentication. An attacker can send malformed LDAP requests to a target Windows system running the LDAP service, typically domain controllers in Active Directory environments.
The vulnerability does not require user interaction, meaning it can be exploited silently. Given the broad deployment of LDAP services in enterprise environments for authentication and directory services, successful exploitation could have cascading effects on organizational infrastructure, disrupting user logins, application authentication, and other LDAP-dependent operations.
Detection Methods for CVE-2024-49121
Indicators of Compromise
- Unexpected crashes or restarts of the LDAP service (lsass.exe or related directory services)
- Windows Event Log entries indicating LDAP service failures or null pointer exceptions
- Network traffic showing malformed or unusual LDAP requests targeting port 389 or 636
- Multiple authentication failures across the domain following LDAP service disruption
Detection Strategies
- Monitor Windows Event Logs for Event ID 1000 (Application Error) related to lsass.exe crashes
- Implement network intrusion detection rules to identify anomalous LDAP traffic patterns
- Deploy endpoint detection and response (EDR) solutions to detect service manipulation and crash patterns
- Enable LDAP debug logging on domain controllers to capture detailed request information
Monitoring Recommendations
- Configure alerts for LDAP service availability and unexpected restarts on domain controllers
- Implement network traffic analysis for LDAP protocols (ports 389/TCP and 636/TCP)
- Monitor for spikes in LDAP connection attempts from external or unusual source IPs
- Establish baseline metrics for LDAP service performance to detect anomalies
How to Mitigate CVE-2024-49121
Immediate Actions Required
- Apply the Microsoft security update for CVE-2024-49121 as soon as possible on all affected systems
- Prioritize patching domain controllers and systems running LDAP services
- Restrict network access to LDAP services (ports 389 and 636) to trusted networks and clients only
- Review firewall rules to limit exposure of LDAP services to untrusted networks
Patch Information
Microsoft has released security updates addressing CVE-2024-49121 as part of their December 2024 Patch Tuesday release. Organizations should consult the Microsoft Security Update Guide for CVE-2024-49121 for specific patch details and download links for their affected Windows versions.
Patches are available for all supported versions of Windows, including Windows 10, Windows 11, and Windows Server editions from 2008 through 2025.
Workarounds
- Implement network segmentation to isolate LDAP services from untrusted network segments
- Configure host-based firewalls on domain controllers to restrict LDAP access to authorized clients
- Deploy load balancing and redundancy for domain controllers to maintain availability during potential attacks
- Consider implementing LDAP request rate limiting at the network perimeter where feasible
# Windows Firewall rule to restrict LDAP access to specific subnet
netsh advfirewall firewall add rule name="Restrict LDAP Access" dir=in action=allow protocol=TCP localport=389 remoteip=192.168.1.0/24
netsh advfirewall firewall add rule name="Restrict LDAPS Access" dir=in action=allow protocol=TCP localport=636 remoteip=192.168.1.0/24
netsh advfirewall firewall add rule name="Block External LDAP" dir=in action=block protocol=TCP localport=389,636
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
