Security researchers have recently discovered a critical vulnerability in the popular open-source multimedia framework, GStreamer. The vulnerability, identified as CVE-2023-37328, allows remote attackers to execute arbitrary code on affected installations via a heap-based buffer overflow that occurs during the parsing of PGS subtitle files. This article discusses the details of this vulnerability, including its exploit and how it can be mitigated. We will also examine the code snippet responsible for the issue and provide references to the original sources.

Exploit Details

The vulnerability occurs due to insufficient validation of the length of user-supplied data before copying it to a heap-based buffer during the parsing of PGS subtitle files. As a consequence, a maliciously-crafted PGS subtitle file can trigger a buffer overflow and lead to code execution in the context of the current process.

It is essential to note that interaction with the GStreamer library is necessary for exploiting this vulnerability. Attack vectors may differ based on the specific use case and implementation of GStreamer in an application.

The following code snippet demonstrates the issue in the GStreamer library

/* Vulnerable code snippet from GStreamer */
void parse_pgs_subtitle(gst_buffer *input) {
  uint8_t *data;
  uint32_t data_len;
  
  data = gst_buffer_map(input, &data_len);
  
  uint32_t subtitle_size;
  memcpy(&subtitle_size, data, sizeof(uint32_t));
  
  /* Buffer overflow vulnerability */
  uint8_t *heap_buffer = (uint8_t *)malloc(subtitle_size);
  memcpy(heap_buffer, data, data_len);
  
  /* Process PGS subtitle data ... */
  
  gst_buffer_unmap(input);
  free(heap_buffer);
}

In this code snippet, the issue arises from the lack of validation of data_len before copying it to the heap-based buffer, heap_buffer, via memcpy() function. A remote attacker can manipulate data_len in a malicious PGS subtitle file to cause a buffer overflow and execute code within the context of the running a process.

Mitigation

To protect against this vulnerability, it is crucial to ensure proper validation of user-supplied data and implement appropriate boundary checks. Developers should also take advantage of available GStreamer security updates and patches.

An example of a secure implementation would be to add a proper boundary check before copying the data into the heap-based buffer:

/* Fixed code snippet with boundary check */
if (subtitle_size >= data_len) {
  memcpy(heap_buffer, data, data_len);
} else {
  // Handle the error case
  return;
}

Original References and Further Reading

For more information on CVE-2023-37328, along with the ZDI-CAN-20994 reference, consult the official sources listed below:

1. CVE-2023-37328: NVD entry
2. GStreamer Official Website
3. ZDI-CAN-20994 Advisory

In conclusion, it's essential to be aware of critical vulnerabilities in widely-used open-source frameworks like GStreamer. Developers must ensure their applications do not expose users to such threats by applying proper validation checks and keeping software updated with the latest security patches.

Timeline

Published on: 05/03/2024 02:15:43 UTC
Last modified on: 06/04/2024 17:24:31 UTC