CVE-2024-56431: Analyzing the invalid negative left shift in oc_huff_tree_unpack function in huffdec.c of libtheora in Theora through 1. 7180717

This post is a detailed analysis of a vulnerability found in the Theora video codec library (CVE-2024-56431). Theora is an open and royalty-free lossy video compression technology. In this particular case, the vulnerability lies in the oc_huff_tree_unpack function in the huffdec.c file and is related to an invalid negative left shift. This affects versions through 1. 7180717 of Theora. We will go through the original references, exploit details, and a code snippet showcasing the vulnerability.

Code Snippet

The problematic code lies in the oc_huff_tree_unpack function in the huffdec.c file of libtheora. The critical part is shown below:

for (j = ; j < OC_NDCT_TOKENS; j++) {
    if (

oc_huff_trees[j].nentries <= oc_pack_read(&opb, _nbits[j])) {
      return TH_EBADHEADER;
    }
    if (oc_huff_tree_unpack(&opb, &oc_huff_trees[j]) < ) {
return TH_EBADHEADER;
    }
  }

This snippet is part of a for-loop, iterating through the OC_NDCT_TOKENS. The oc_huff_trees array has nentries, and each entry has an invalid negative left shift.

The original advisory for this vulnerability can be found in the following link

- Theora Advisory

Exploit Details

This vulnerability is caused by an invalid negative left shift in the oc_huff_tree_unpack function. An attacker can exploit this issue by crafting a Theora video file with a malicious payload to trigger this vulnerability. When a user attempts to play this video, the vulnerability could be exploited to cause a denial of service (DoS), or potentially execute arbitrary code on the target system.

Attack Scenario

1. Attacker crafts a malicious Theora video file embedding a specially crafted payload to trigger the invalid negative left shift.

Victim downloads and opens the malicious Theora video file using a Theora compatible video player.

3. The vulnerable function is called when decoding the video, resulting in a denial of service or possible arbitrary code execution on the victim's system.

Mitigation Measures

The Theora team has addressed this vulnerability in newer versions of the libtheora library. Users are advised to upgrade to the latest version as soon as possible to avoid potential security risks.

For detailed patch information, refer to the original advisory

- Theora Patch

Conclusion

This post has provided an analysis of the CVE-2024-56431 vulnerability, affecting the Theora video codec library. The key takeaway here is the importance of keeping your libraries up to date, especially those that deal with decoding or processing media files, as these are often the target of exploitation. By staying vigilant and keeping your software current, you can help protect your systems from such threats.

Timeline

Published on: 12/25/2024 17:15:05 UTC
Last modified on: 02/18/2025 22:15:13 UTC