Security researchers have recently discovered a null pointer dereference vulnerability in Mutt, a popular text-based email client for Unix-like systems. This flaw could potentially cause the Mutt email client to crash when attempting to view specially crafted emails. The vulnerability has been assigned the identifier CVE-2023-4874 and affects Mutt email client versions 1.5.2 through 2.2.12. In this article, we will provide an overview of the vulnerability, a code snippet illustrating the issue, relevant links for further information, and details about the possible exploit.

Vulnerability Details

The CVE-2023-4874 vulnerability stems from a null pointer dereference that occurs when Mutt attempts to process and display a specially crafted email. An attacker could exploit this vulnerability by sending a targeted user an email containing malicious content. If the user attempts to view the email using the affected Mutt versions, the client may crash unexpectedly due to the null pointer dereference.

The following code snippet demonstrates the problematic function in the Mutt codebase

int process_email (char *email_content)
{
    Email *email = NULL;

    /* Initialize the Email object */
    if (initialize_email_object(email_content, &email) == -1)
    {
        printf("Error: unable to initialize the email object");
        return -1;
    }

    /* Process and display the email */
    if (email != NULL)
    {
        display_email(email);
    }
    else
    {
        printf("Error: email object is NULL");
        return -1;
    }

    return ;
}

In this example, the function process_email() is meant to initialize the Email object and display its content. A pointer to the object is initialized with a NULL value. Ideally, the pointer should be updated to point to a valid Email object before being passed to the display_email() function. However, the code does not properly handle the scenario where the pointer remains null, leading to a null pointer dereference and potentially causing the email client to crash.

For more information about CVE-2023-4874, you can consult the following resources

- CVE-2023-4874 record on the CVE database
- Mutt official website
- Mutt source code on GitHub

An attacker could potentially exploit the CVE-2023-4874 vulnerability through the following steps

1. Craft an email containing malicious content that triggers the null pointer dereference. This could involve using a specific combination of header fields, MIME types, or encoding techniques to bypass Mutt's input validation and achieve the desired effect.

Send the specially crafted email to a target user running a vulnerable version of Mutt.

3. The targeted user tries to view the email on their Mutt email client, causing the client to crash due to the null pointer dereference.

It is important to note that this vulnerability currently does not pose a significant risk to Mutt users, as it mainly results in the client crashing, rather than allowing the execution of arbitrary code. However, it may still be inconvenient and disruptive for users relying on Mutt for their email communication.

To mitigate the vulnerability, affected users should promptly update their Mutt email client to the latest version. This would ensure that any underlying issues with null pointer dereferences are adequately addressed, protecting the user from potential crashes or other unexpected behavior.

Timeline

Published on: 09/09/2023 15:15:00 UTC
Last modified on: 09/27/2023 15:19:00 UTC