Security researchers have recently discovered a critical security vulnerability in the _imagingcms.c module of the widely used Python imaging library Pillow, notably affecting versions before 10.3.. This vulnerability has been given the identifier CVE-2024-28219 and is caused by a buffer overflow due to the improper use of strcpy() when strncpy() should have been used instead. This blog post aims to provide an in-depth look at this vulnerability, including code snippets, original references, and exploitation details.

Overview of the vulnerability

A buffer overflow, one of the most dreaded bugs in the programming world, can lead to arbitrary code execution, denial of service, or information disclosure attacks. In the case of CVE-2024-28219, the vulnerability exists within the _imagingcms.c module of Pillow, specifically in the function that handles the conversion of image file names.

The problematic code snippet in the _imagingcms.c module can be seen below

    // ...
    char fileName[MAX_PATH + 1];
    // ...
    strcpy(fileName, PyUnicode_AsUTF8(fnamebuf));
    // ...

As shown above, the code uses strcpy() to copy the source string to the destination buffer. Unfortunately, strncpy() should have been used instead to ensure that the copying process does not exceed the size of the destination buffer and prevent the buffer overflow.

The fixed code snippet should look like the following

    // ...
    char fileName[MAX_PATH + 1];
    // ...
    strncpy(fileName, PyUnicode_AsUTF8(fnamebuf), MAX_PATH);
    // ...

By using strncpy() with the proper size limit, the code ensures that the copied data will never exceed the buffer size, mitigating the buffer overflow vulnerability.

1. Pillow's official GitHub repository: https://github.com/python-pillow/Pillow
2. Pillow Security Advisory: https://github.com/python-pillow/Pillow/security/advisories/GHSA-98q8-65gg-wrfq
3. CVE Details for CVE-2024-28219: https://www.cvedetails.com/cve/CVE-2024-28219/
4. NVD - National Vulnerability Database: https://nvd.nist.gov/vuln/detail/CVE-2024-28219

Exploit details

An attacker who successfully exploits this vulnerability can potentially execute arbitrary code on the affected system. To exploit CVE-2024-28219, an attacker needs to craft a malicious image file with a file name long enough to trigger the buffer overflow and then convince the victim to open or process the malformed image using an application built with a compromised version of Pillow.

In conclusion, it is of critical importance that all users of affected versions of Pillow update to the latest version (10.3. or later) immediately to protect their systems from this vulnerability. Developers utilizing Pillow in their applications should also ensure they are using the patched version to prevent exploitation. Remember, always keep your software up to date, and stay vigilant for security risks.

Timeline

Published on: 04/03/2024 03:15:09 UTC
Last modified on: 04/10/2024 22:15:07 UTC