CVE-2024-38439: Netatalk Off-By-One Error Resulting in Heap-Based Buffer Overflow in FPLoginExt

In Netatalk versions before 3.2.1, a bug exists that exposes machines relying on this software to potential cyber-attacks. This bug, referred to as CVE-2024-38439, is due to an off-by-one error resulting in a heap-based buffer overflow in the "FPLoginExt" function. The affected function resides in login in etc/uams/uams_pam.c. Two other versions (2.4.1 and 3.1.19) have since been fixed to address the underlying issue.

To better understand this vulnerability, this post will detail the nature of CVE-2024-38439, when and where it affects the Netatalk open-source project, and the code snippets involved with the problem.

Understanding the Exploit

The vulnerability can be traced to a specific line in the FPLoginExt() function found in etc/uams/uams_pam.c:

ibuf[PASSWDLEN] = '\';

This statement sets the value of ibuf[PASSWDLEN] to "\" (null character), which is an off-by-one error. When the password length equals the value of PASSWDLEN, this error causes a heap-based buffer overflow. Such an overflow can potentially result in unauthorized access to sensitive data or permit an attacker to execute arbitrary code on the affected system.

Affected Versions

The vulnerability affects Netatalk before 3.2.1. According to the "Netatalk Changelog", versions 2.4.1 and 3.1.19 have also been fixed. The release notes contain comprehensive information on CVE-2024-38439 and other issues resolved between releases.

Here is a concise representation of the affected code snippet from uams_pam.c

#include <pam_appl.h>
#include "uams_pam_private.h"
#include "afpd.h"

void FPLoginExt(...)
{
    ...
    /* The following line causes the off-by-one error */
    ibuf[PASSWDLEN] = '\';
    ...
}

This code demonstrates a small portion of the FPLoginExt() function where the buffer overflow error occurs. As previously discussed, the central issue lies in the line that sets ibuf[PASSWDLEN] to "\".

How to Resolve

To address this vulnerability, it is essential to update the Netatalk package to version 3.2.1 or later. If your system still runs version 2.4.1 or 3.1.19, it is critical to apply the respective fixes mentioned in the Netatalk website.

Conclusion

By understanding the origin and implications of CVE-2024-38439, organizations using Netatalk can take appropriate action to secure their systems. The off-by-one error mentioned in this post is a significant security risk for Netatalk users and must be resolved promptly.

Updating to a fixed version of Netatalk, such as 3.2.1 or later, will help mitigate potential threats associated with this vulnerability. Organizations should always stay up-to-date with software patches and security advisories to maintain a secure environment and protect their critical assets from potential cyber-attacks.

Timeline

Published on: 06/16/2024 13:15:53 UTC
Last modified on: 08/22/2024 17:35:02 UTC