The Common Vulnerabilities and Exposures (CVE) system has recently identified a memory leak vulnerability within Kerberos 5 (also known as krb5) v1.21.2. This vulnerability, registered as CVE-2024-26458, can pose a significant risk to the integrity and stability of systems relying on Kerberos for authentication and authorization.

Kerberos is a widely used, open-source network authentication protocol that allows nodes to securely authenticate within a network environment. The vulnerability in question resides in the /krb5/src/lib/rpc/pmap_rmt.c file, which contains a critical memory leak.

In this blog post, we will delve into the specifics of this vulnerability, providing code snippets showing the issue, links to original references, and exploit details. We will also share recommendations on how to mitigate this vulnerability.

Code Snippet Highlighting the Vulnerability

The vulnerability resides in the pmap_rmt.c file, which is part of the RPC library used by Kerberos. The memory leak occurs in the following section of the code:

 // /krb5/src/lib/rpc/pmap_rmt.c

 void pmap_rmtcall(CLIENT *client, struct rmtcallargs *a, struct rmtcallres *r)
 {
 ...
   if (clnt_call((CLIENT *) client, ...))
   {
       // Handle error case
   }
 ...
 }

In this snippet, the error handling is not properly cleaning up allocated memory, resulting in a memory leak. This leak can potentially be exploited by an attacker, leading to the exhaustion of system resources.

Exploit Details

An attacker may exploit this vulnerability by repeatedly sending specially crafted requests to the affected Kerberos instance, causing the memory leak in the pmap_rmt.c file to persistently allocate memory without releasing it. Over time, this could result in a significant amount of memory being consumed, ultimately causing system instability or even a crash.

While no known public exploits currently exist for CVE-2024-26458, the potential impact of this vulnerability should not be taken lightly. Organizations relying on the affected version of Kerberos are encouraged to take immediate action to mitigate the risk posed by this vulnerability.

Original References

1. MIT Kerberos 5 Security Advisory
2. National Vulnerability Database - CVE-2024-26458

To minimize the risk posed by CVE-2024-26458, we recommend taking the following steps

1. Upgrade to the patched version of Kerberos 5 (krb5), v1.21.3 or later, which addresses the memory leak vulnerability. The latest version can be found on the MIT Kerberos project's GitHub repository.

2. Monitor your systems closely for any signs of unusual resource consumption, especially memory usage. Implement performance monitoring tools to keep track of memory usage and detect potential issues before they escalate.

3. Continually assess and update your organization's security posture, ensuring that security best practices are followed, and staff are trained in identifying and mitigating potential security risks.

Conclusion

CVE-2024-26458 highlights a critical vulnerability in Kerberos 5, with the potential for significant impact to systems relying on this authentication protocol. While no known public exploits currently exist, organizations should take immediate action to mitigate the risk posed by this memory leak. By upgrading to a patched version of Kerberos 5 and monitoring system resources, organizations can help safeguard the integrity and stability of their network environment.

Timeline

Published on: 02/29/2024 01:44:18 UTC
Last modified on: 05/14/2024 15:09:00 UTC