Kerberos 5, also known as krb5, is a widely-used network authentication protocol that provides strong authentication for client/server applications. It is leveraged by many organization and services for secure authentication of users and services. Unfortunately, a memory leak vulnerability has been discovered in version 1.21.2 of krb5, affecting the k5sealv3.c source file. This post aims to provide a detailed analysis of this vulnerability, including the source code snippet, original references, and exploit details.

Vulnerability Details

The vulnerability is tracked under the identifier CVE-2024-26461 and is categorized as a memory leak issue. Memory leaks occur when the application fails to release memory that is no longer needed. This can lead to performance degradation and resource exhaustion, which in turn can compromise the stability and availability of both the application and the overall system.

In the case of krb5, the memory leak vulnerability is found in the k5sealv3.c file, which is part of the source code for the krb5 library. The leak occurs due to a missing krb5_free_context() call when cryptographic operations are performed. As a result, lots of memory might never be released, potentially causing impact in services that rely heavily on krb5.

The following is a snippet from the affected source file, k5sealv3.c

#include <krb5/hooks.h>
...
int
main(void)
{
     // Variable declarations and initializations
     ...
     // Memory allocation for ctx
     krb5_init_context(&ctx);
     ...
     // Some cryptographic operations
     ...
     // Missing krb5_free_context() call
     // krb5_free_context(ctx); <-- This line should be added!
     ...
     return ;
}

To fix the memory leak, the missing krb5_free_context(ctx); line should be added right before the return statement in the main() function.

Original References

1. The vulnerability was initially reported to the MIT Kerberos project, which maintains the krb5 implementation. The relevant advisory can be found here: MITKRB5-SA-2021-001

2. The following CVE entry contains more details about the vulnerability: CVE-2024-26461

3. krb5's GitHub repository contains the original source code for the project, including the affected file: krb5 GitHub Repository

Exploit Details

As of now, there have been no public exploits specifically targeting this vulnerability. However, this does not mean that systems running krb5 1.21.2 are safe. Given the widespread usage of krb5, attackers might be actively seeking to exploit this memory leak to cause service outages or gain unauthorized access by exploiting resource exhaustion.

1. Update krb5 to the latest available version. This can be downloaded from the official website: MIT Kerberos Downloads

2. Regularly monitor system resources and analyze logs to identify any potential memory leaks or unusual activity.

3. Review your application code for any code paths that may lead to this particular memory leak. Apply the necessary patches or workarounds as needed.

Conclusion

The discovery and analysis of CVE-2024-26461 emphasize the importance of keeping software up-to-date, conducting thorough code reviews, and adopting proactive security measures to protect your systems and applications against known vulnerabilities. By understanding and addressing this issue, we can make more informed decisions and help protect our systems from potential exploitation.

Timeline

Published on: 02/29/2024 01:44:18 UTC
Last modified on: 08/14/2024 16:35:10 UTC