Abstract
The Lightweight Directory Access Protocol (LDAP) is a widely used protocol for accessing and managing directory services, such as those provided by Microsoft Active Directory (AD). While LDAP servers are often the focus of security discussions, LDAP clients—software components that initiate connections to LDAP servers—are also susceptible to vulnerabilities that can be exploited by attackers. This paper examines CVEs that specifically target LDAP clients, detailing their mechanisms, impacts, and mitigation strategies. Notable examples, such as CVE-2024-49112 and CVE-2022-29128, are analyzed to illustrate the risks posed to LDAP clients in modern network environments.
Introduction
LDAP clients are integral to directory service operations, enabling applications and systems to query and authenticate against directory servers. These clients, typically implemented in libraries like wldap32.dll on Windows or OpenLDAP’s libldap on Unix-based systems, communicate over ports such as 389 (LDAP) or 636 (LDAPS). While much attention is given to securing LDAP servers, vulnerabilities in LDAP clients can equally compromise network security by allowing remote code execution (RCE), denial-of-service (DoS), or data leaks.
The Common Vulnerabilities and Exposures (CVE) system catalogs such security flaws, providing a standardized way to identify and address them. This paper explores CVEs that directly attack LDAP clients, focusing on their exploitation paths and the broader implications for enterprise security. By understanding these vulnerabilities, organizations can better protect their LDAP-dependent systems.
LDAP Client Vulnerabilities: Overview and Examples
LDAP client vulnerabilities typically arise from flaws in how clients process server responses, handle input validation, or manage network protocols. Below are detailed examples of CVEs that target LDAP clients, drawn from recent disclosures and historical records.
CVE-2024-49112: Windows LDAP Remote Code Execution
- Description: Disclosed by Microsoft on December 10, 2024, CVE-2024-49112 is a critical RCE vulnerability in the Windows LDAP client (
wldap32.dll) with a CVSS score of 9.8. It results from an integer overflow that can be triggered by a malicious LDAP server response. - Exploitation: An attacker crafts a Connectionless LDAP (CLDAP) referral response to exploit this flaw. The attack begins with a DCE/RPC request that triggers a DNS SRV query, followed by NBNS spoofing to direct the client to a malicious LDAP server. The malformed response then causes the overflow, enabling code execution within the LDAP service context.
- Impact: This vulnerability allows unauthenticated attackers to execute arbitrary code on any Windows system acting as an LDAP client, including Domain Controllers and workstations, provided the DNS server has internet connectivity.
- Reference: Microsoft Security Update Guide, CVE-2024-49112
CVE-2022-29128: Windows LDAP Remote Code Execution
- Description: Patched in May 2022, CVE-2022-29128 is an RCE vulnerability affecting the Windows LDAP client, with a CVSS score of 9.8. It occurs due to insufficient validation of server responses when processing LDAP queries.
- Exploitation: An attacker tricks a victim into connecting to a malicious LDAP server (e.g., via phishing or DNS manipulation). The server sends a crafted response that exploits the client’s parsing logic, allowing arbitrary code execution.
- Impact: This flaw targets LDAP client applications, potentially compromising workstations or servers that initiate LDAP connections, even if they are not Domain Controllers.
- Reference: Microsoft Security Update Guide, CVE-2022-29128
CVE-2024-49113: Windows LDAP Denial of Service
- Description: Also disclosed in December 2024 alongside CVE-2024-49112, CVE-2024-49113 is a DoS vulnerability in the Windows LDAP client with a CVSS score of 7.5. It shares a similar root cause—an integer overflow in
wldap32.dll. - Exploitation: The attack mirrors CVE-2024-49112’s chain: a DCE/RPC request leads to a malicious CLDAP referral response, crashing the Local Security Authority Subsystem Service (LSASS) and forcing a system reboot. SafeBreach Labs’ “LDAPNightmare” PoC demonstrates this exploit.
- Impact: While not an RCE, this vulnerability disrupts LDAP client operations, affecting availability on unpatched systems.
- Reference: SafeBreach Labs, LDAPNightmare Exploit
Historical Context: OpenLDAP Client Vulnerabilities
- Example: Older OpenLDAP vulnerabilities, such as those prior to version 2.4.50 (e.g., CVE-2020-12243), highlight risks in open-source LDAP clients. These include denial-of-service flaws caused by improper handling of BER (Basic Encoding Rules) data from malicious servers.
- Exploitation: An attacker sends crafted LDAP responses to trigger memory corruption or crashes in the client’s
libldaplibrary. - Impact: These flaws primarily affect Unix-based systems using OpenLDAP, demonstrating that LDAP client vulnerabilities are not exclusive to Windows.
- Reference: CVE Details, OpenLDAP Vulnerabilities
Attack Vectors and Exploitation Techniques
LDAP client attacks typically exploit the client-server trust relationship. Common techniques include:
- Malicious Server Responses: Attackers set up rogue LDAP servers to send malformed data, exploiting flaws in client parsing (e.g., CVE-2024-49112, CVE-2022-29128).
- DNS and Network Manipulation: Spoofing DNS or NBNS responses redirects clients to attacker-controlled servers, as seen in “LDAPNightmare.”
- Social Engineering: Tricking users or applications into querying a malicious server, a method noted in CVE-2022-29128.
These vectors require no direct access to the client system, only the ability to influence its network interactions, making them particularly insidious.
Impact on Network Security
LDAP client vulnerabilities can compromise entire networks due to their role in authentication and directory access:
- Privilege Escalation: RCE vulnerabilities like CVE-2024-49112 can grant attackers SYSTEM-level access, especially on Domain Controllers.
- Service Disruption: DoS flaws (e.g., CVE-2024-49113) interrupt critical services, affecting user authentication and system availability.
- Data Exposure: Compromised clients may leak sensitive directory data if exploited during authentication workflows.
The widespread use of LDAP in enterprise environments amplifies these risks, as a single vulnerable client can serve as an entry point for broader attacks.
Mitigation Strategies
To protect LDAP clients from these CVEs, organizations should adopt the following measures:
- Patch Management: Apply security updates promptly. For instance, Microsoft’s December 2024 patches resolve CVE-2024-49112 and CVE-2024-49113.
- Network Controls: Restrict LDAP client connections to trusted servers and block outbound traffic to unverified domains.
- Encryption: Use LDAPS (port 636) to encrypt communications, reducing the risk of interception or downgrade attacks.
- Monitoring: Detect suspicious DNS queries, NBNS responses, or CLDAP traffic indicative of exploitation attempts.
- Least Privilege: Limit client applications’ permissions to minimize damage from potential exploits.
Conclusion
Yes, there are CVEs that can attack LDAP clients, with notable examples like CVE-2024-49112 and CVE-2022-29128 demonstrating the potential for remote code execution, and CVE-2024-49113 showing denial-of-service risks. These vulnerabilities exploit flaws in client-side LDAP implementations, often requiring minimal attacker effort beyond controlling a malicious server or network responses. As LDAP remains a critical protocol in directory services, securing clients against such threats is paramount. By understanding these CVEs and implementing robust defenses, organizations can safeguard their networks from exploitation.
References
- Microsoft Security Response Center. (2024). “CVE-2024-49112: Windows Lightweight Directory Access Protocol (LDAP) Remote Code Execution Vulnerability.” https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-49112
- SafeBreach Labs. (2025). “LDAPNightmare: Exploiting CVE-2024-49113.” https://www.safebreach.com/blog/ldapnightmare-exploit-cve-2024-49113
- Microsoft Security Update Guide. (2022). “CVE-2022-29128: Windows LDAP Remote Code Execution Vulnerability.” https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-29128
- CVE Details. (n.d.). “OpenLDAP Security Vulnerabilities.” https://www.cvedetails.com/vulnerability-list/vendor_id-173/Openldap.html
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