CVE-2022-43245: Exploring the Segmentation Violation in Libde265 v1..8 that Leads to Denial of Service

A newly discovered security vulnerability, CVE-2022-43245, was found in libde265 v1..8, which is an open-source library that implements the HEVC (High-Efficiency Video Coding) video coding standard. This vulnerability constitutes a segmentation violation that occurs during the apply_sao_internal implementation in the sao.cc file. As a result, this vulnerability can be exploited by an attacker to cause a Denial of Service (DoS) attack through a specially crafted video file. In this post, we will take a deeper look into the technical details of this vulnerability and show some code snippets illustrating the issue.

Vulnerability Overview

The CVE-2022-43245 vulnerability occurs in the apply_sao_internal function in the sao.cc source code file. The libde265 library's main purpose is to decode HEVC (mpeg-H or h.265) video streams, and the Scalable Adaptive Offset (SAO) module specifically processes SAO filters, a critical video encoding/decoding feature in HEVC.

Below is a simplified code snippet from the vulnerable function in sao.cc

template <>
void apply_sao_internal<uint16_t>(const de265_image* img_src,
                                  de265_image* img_dst,
                                  int  x, int  y,
                                  int sao_type,
                                  int idx,
                                  const int sao_offset[]) {
  ...
  for (int y = blockIdx_y * blockDim.y + threadIdx.y; y < height; y += blockDim.y * gridDim.y) {
    for (int x = blockIdx_x * blockDim.x + threadIdx.x; x < width; x += blockDim.x * gridDim.x) {
      ...
      uint16_t src_value = input_image->get_pel(xpos, ypos, channel);
      ...
      new_value = src_value + sao_offset[table_idx];
      if (new_value > 255) { new_value = 255; }
      if (new_value < )   { new_value = ; }

      dst_img->set_pel(xpos, ypos, channel, (uint8_t)new_value);
    }
  }
}

What makes this function vulnerable is that the potential for segmentation violation occurs during input and output operations related to certain memory allocations. An attacker can craft a particular video file that, when processed by the libde265 library, can lead to an out-of-bounds memory access, causing a segmentation violation. This can result in the disruption of the encoding/decoding process, ultimately leading to a Denial of Service (DoS) attack.

Original References

* The libde265 v1..8's GitHub repository, including the source code containing the CVE-2022-43245 vulnerability, can be found here: https://github.com/strukturag/libde265
* More information about the HEVC video coding standard, which libde265 implements, can be found at the official website: https://en.wikipedia.org/wiki/High_Efficiency_Video_Coding

Exploiting the Vulnerability

The actual exploit would involve crafting a malicious video file that piggybacks on the vulnerable apply_sao_internal<unsigned short> function in the sao.cc file. By providing specific input parameters that enable out-of-bounds memory access, an attacker would be able to cause the software to crash, leading to Denial of Service (DoS) in the target application. However, we won't provide the specific steps to craft such a video file to prevent the misuse of this information.

Mitigation and Conclusion

Mitigating this CVE-2022-43245 vulnerability requires patching or updating the libde265 v1..8 library. Developers should keep an eye on the library's GitHub repository for any vital security updates and patches, while users are advised to update their software that relies on the libde265 library as soon as an update becomes available.

To sum up, this post explored the technical details of the CVE-2022-43245 vulnerability discovered in libde265 v1..8, which allows attackers to cause a Denial of Service (DoS) attack through a specially crafted video file. By understanding the specifics of this vulnerability, developers and users can make informed decisions on updating their software or adopting safer alternatives to protect themselves from potential threats.

Timeline

Published on: 11/02/2022 14:15:00 UTC
Last modified on: 02/27/2023 15:25:00 UTC