CVE-2024-49112: A Critical Remote Code Execution Vulnerability in Windows LDAP

Introduction

The Lightweight Directory Access Protocol (LDAP) is a foundational protocol used in directory services like Microsoft’s Active Directory (AD) to manage authentication, authorization, and resource access in enterprise networks. LDAP enables querying and modifying directory information, making it essential for identity management in Windows environments. However, its critical role also makes it a prime target for attackers, and vulnerabilities in LDAP implementations can have severe consequences.

One such vulnerability, CVE-2024-49112, was disclosed by Microsoft in December 2024 as part of their monthly Patch Tuesday updates. This critical flaw, with a CVSS score of 9.8, allows unauthenticated attackers to execute arbitrary code remotely on vulnerable systems, posing a significant risk to organizations relying on Active Directory for network management.

For more background on Active Directory and LDAP, refer to Microsoft’s official documentation:

What is CVE-2024-49112?

CVE-2024-49112 is a Remote Code Execution vulnerability located in the Windows LDAP client, specifically within the wldap32.dll library. The flaw is caused by an integer overflow that can be triggered by sending specially crafted LDAP requests to a vulnerable system. Alarmingly, this vulnerability does not require authentication, meaning an attacker can exploit it remotely without credentials, potentially gaining full control over the affected system.

Discovered by security researcher Yuki Chen and patched by Microsoft in December 2024, CVE-2024-49112 affects a wide range of Windows Server versions, including:

  • Windows Server 2008 SP2
  • Windows Server 2008 R2 SP1
  • Windows Server 2012 and 2012 R2
  • Windows Server 2016
  • Windows Server 2019
  • Windows Server 2022
  • Certain Windows 10 versions (e.g., 1607, 1809)

For detailed information on the vulnerability, see:

Exploitation Mechanism

Exploiting CVE-2024-49112 involves a sophisticated multi-step attack chain that manipulates how Windows processes LDAP referral responses. The following outlines the key steps in the exploitation process:

  1. DCE/RPC Request: The attacker sends a crafted DCE/RPC (Distributed Computing Environment/Remote Procedure Call) request to the target server, prompting it to issue a DNS SRV (Service) query for a domain under the attacker’s control.
  2. DNS Response Manipulation: The attacker’s DNS server responds with a hostname and LDAP port that point to a malicious LDAP server, tricking the target into connecting to it.
  3. NBNS Spoofing: The target server broadcasts a NetBIOS Name Service (NBNS) request to resolve the hostname. The attacker spoofs the response, directing the server to their IP address.
  4. Malicious CLDAP Referral: When the target connects to the attacker’s LDAP server, it receives a Connectionless LDAP (CLDAP) referral response containing malformed data. This triggers the integer overflow in the LDAP client library, leading to either a system crash or arbitrary code execution.

A proof-of-concept (PoC) exploit named “LDAPNightmare” was developed by SafeBreach Labs and released in January 2025. This PoC demonstrates how the vulnerability can be used to crash unpatched Windows servers, including Domain Controllers, by delivering a malicious CLDAP referral. While the publicized version focuses on denial-of-service (DoS), security experts warn that slight modifications could enable full RCE.

For a detailed breakdown of the exploit, see:

Impact of CVE-2024-49112

The exploitation of CVE-2024-49112 can have devastating effects on affected systems and networks, particularly those relying on Active Directory. Key impacts include:

  • System Compromise: Successful exploitation allows attackers to execute arbitrary code with the privileges of the LDAP service, which often runs with SYSTEM-level access on Domain Controllers. This can lead to complete control over the affected machine.
  • Lateral Movement: A compromised server, especially a Domain Controller, can be used as a foothold for attackers to move laterally within the network, targeting additional systems and sensitive data.
  • Service Disruption: Even without achieving code execution, the exploit can crash critical servers, disrupting authentication and other essential services.
  • Data Breaches: Control over an LDAP server could enable attackers to extract sensitive directory information, such as user credentials and group memberships, facilitating further attacks like privilege escalation or data exfiltration.

Given its CVSS score of 9.8 and the availability of public exploit code, CVE-2024-49112 represents an immediate and severe threat to unpatched systems.

For more on the potential impact, refer to:

Affected Systems

CVE-2024-49112 affects a broad range of Windows Server editions, both standard and Server Core installations, including:

  • Windows Server 2008 SP2
  • Windows Server 2008 R2 SP1
  • Windows Server 2012 and 2012 R2
  • Windows Server 2016
  • Windows Server 2019
  • Windows Server 2022
  • Selected Windows 10 versions (e.g., 1607, 1809)

While Domain Controllers are the primary targets due to their LDAP services, any Windows Server with an internet-connected DNS server is vulnerable because the exploit targets the LDAP client functionality.

Related Vulnerability: CVE-2024-49113

In the same December 2024 Patch Tuesday update, Microsoft also addressed CVE-2024-49113, a related denial-of-service (DoS) vulnerability in Windows LDAP with a CVSS score of 7.5. Like CVE-2024-49112, this flaw is caused by an integer overflow and can be exploited to crash systems. Although less severe, it complements the RCE threat and should be mitigated alongside CVE-2024-49112.

For more information on CVE-2024-49113, see:

Mitigation and Best Practices

Protecting against CVE-2024-49112 requires immediate action and a multi-layered security approach. The following mitigation strategies are recommended:

  1. Patch Immediately: Apply Microsoft’s December 2024 security updates to all affected systems as soon as possible. Prioritize patching Domain Controllers and other critical servers to close the vulnerability.
  1. Monitor for Exploitation: Implement monitoring for signs of attempted exploitation, such as:
  • Unusual DCE/RPC requests
  • Suspicious DNS SRV queries
  • Anomalous NBNS responses
  • Unexpected CLDAP referral traffic
  • SafeBreach Labs has published indicators of compromise (IoCs) to aid in detection: SafeBreach Labs: LDAPNightmare IoCs
  1. Network Segmentation: Limit internet access for critical systems and isolate LDAP services from untrusted networks to reduce exposure.
  2. Disable Unnecessary Services: If LDAP functionality is not required on a server, disable it to eliminate the attack vector.
  3. Secure LDAP Communications: Use LDAPS (LDAP over SSL/TLS) to encrypt traffic and prevent tampering.
  1. Conduct Vulnerability Assessments: Regularly scan systems to ensure patches are applied and to identify any remaining risks.

For additional LDAP security best practices, refer to:

Conclusion

CVE-2024-49112 is a critical vulnerability that poses a significant risk to organizations using Windows Server and Active Directory. Its ability to allow unauthenticated remote code execution, combined with the availability of public exploit code, makes it a high-priority target for attackers. By applying patches promptly, enhancing network monitoring, and following security best practices, organizations can mitigate the risks posed by this vulnerability. As cyber threats continue to evolve, proactive measures are essential to safeguarding critical infrastructure.

※ This article is written by Grok. Fact-checking is required.