CVE-2024-8184: Jetty's ThreadLimitHandler.getRemote() Vulnerability - Understanding the Exploit and How to Prevent Remote DoS Attacks

Introduction: In recent security research, a critical vulnerability (CVE-2024-8184) has been discovered in Jetty's ThreadLimitHandler.getRemote() method. This vulnerability exposes Jetty servers to potential remote denial-of-service (DoS) attacks. In this post, we'll dive into the details of this vulnerability, explore ways it can be exploited, and discuss how to protect your systems from this threat.

Vulnerability Overview: Jetty's ThreadLimitHandler.getRemote() method does not properly handle specific requests. As a result, malicious actors can trigger OutofMemory errors by repeatedly sending crafted requests. Ultimately, this vulnerability allows attackers to exhaust server memory, leading to a remote denial-of-service (DoS) attack.

Exploit Details: The vulnerability can be exploited by sending crafted requests to the vulnerable server with specific headers. This will cause the server to under-estimate the number of threads being requested, allowing the attacker to repeatedly send requests and consume large amounts of server memory. The code snippet below demonstrates the key part of this vulnerability:

...
private InetAddress getRemote(InetAddress remote)
{
    InetAddress limited = _map.get(remote.getAddress());
    if (limited!=null)
        return limited;
    byte[] addr = remote.getAddress();
    addr = Arrays.copyOf(addr, addr.length);
    limited = InetAddress.getByAddress(addr);
    if (_map.putIfAbsent(addr, limited)!=null)
        _map.get(addr);
    return limited;
}
...

The issue lies in the usage of the ConcurrentHashMap's putIfAbsent method. Given the specific crafted requests, this method returns a null value, causing a NullPointerException and allowing attackers to exhaust server memory with a high number of threads.

Original References: Jetty's Github Repository, CVE-2024-8184

Mitigation Techniques: There are multiple ways to protect your Jetty server from this vulnerability

1. Update your Jetty server to the latest version. Keep an eye on Jetty's Github repository for important updates, and ensure that your servers always have the latest security patches installed.

2. Implement a rate limiter to restrict the number of requests from any single IP address in a given period. This can help in preventing attackers from overwhelming your server with repeated requests.

3. Regularly monitor your server logs. Pay attention to any unusual patterns or high numbers of requests coming from specific IP addresses. Investigate any suspicious activities and block malicious users accordingly.

4. Set up automatic alerts and thresholds to notify you when server memory usage reaches critical levels. Proactively intervene and investigate in response to such alerts to prevent potential DoS attacks.

Conclusion: The CVE-2024-8184 vulnerability in Jetty's ThreadLimitHandler.getRemote() method puts systems at risk for remote denial-of-service (DoS) attacks. By understanding the exploit and implementing preventative measures, you can protect your systems from unauthorized users looking to cause serious harm. Stay informed and up-to-date on all Jetty and security-related updates to minimize the potential impact of this and other vulnerabilities on your systems.

Timeline

Published on: 10/14/2024 16:15:04 UTC
Last modified on: 11/08/2024 21:00:09 UTC