CVE-2023-4050 - Untrusted Input Stream Stack Buffer Overflow Vulnerability in Firefox

A new security vulnerability, CVE-2023-4050, has been discovered in Mozilla Firefox. In certain situations, an untrusted input stream was copied to a stack buffer without checking its size. Consequently, this led to a potentially exploitable crash, which could have allowed an attacker to escape the sandbox and take over control of an affected system. Mozilla Firefox (versions prior to 116), Firefox ESR (versions prior to 102.14), and Firefox ESR (versions prior to 115.1) are all impacted by this vulnerability.

Exploit Details

This stack buffer overflow vulnerability occurs when an untrusted input stream is copied to a stack buffer without verifying its size. A stack buffer is a region of memory reserved to hold temporary data required during function execution. When a larger input stream than the buffer size is provided, it can cause a crash, leading to potential exploitation.

The vulnerability lies in the way Firefox handles certain untrusted input streams. Upon receiving the input, Firefox should have both validated the input size and made sure that the input does not exceed the size of the receiving buffer. However, due to a flaw in Firefox's implementation, this validation is not performed, leading to a potential stack buffer overflow.

Here's a simplified code snippet that demonstrates the issue

#include <stdio.h>
#include <string.h>

void vulnerable_function(char *input) {
  char stack_buffer[64];

  /* Copy input to stack_buffer without checking its size */
  strcpy(stack_buffer, input);
}

int main() {
  char large_input[128];

  /* Fill the large_input array with 'A' characters */
  memset(large_input, 'A', sizeof(large_input) - 1);
  large_input[sizeof(large_input) - 1] = ;  // null-terminate the string

  /* Pass the large_input string to the vulnerable function */
  vulnerable_function(large_input);

  return ;
}

In the above example, a stack buffer of size 64 bytes is declared in the vulnerable_function function. The function reads input without checking its size and copies it into the stack buffer using strcpy. This could result in a stack buffer overflow when the input size exceeds the buffer capacity.

Original References

Mozilla has acknowledged this vulnerability in its security advisories and has released patches for the affected Firefox versions to address it. For more information, see the Mozilla Security Advisory pages for each affected version:

- Firefox version 116
- Firefox ESR version 102.14
- Firefox ESR version 115.1

Mitigation

Users are advised to update their Firefox installations to the latest version as soon as possible to protect against this vulnerability:

Update Firefox ESR to version 115.1 or later

You can download the latest version of Firefox from the official Mozilla website, or use the built-in Firefox updater to apply the updates.

Conclusion

The CVE-2023-4050 vulnerability in Firefox is a serious security issue that could lead to a sandbox escape if exploited. It is essential for users to update their Firefox installations to the latest version to mitigate this vulnerability and prevent potential exploitation. Always be vigilant and ensure your software is up-to-date to protect your systems and data from threats.

Timeline

Published on: 08/01/2023 15:15:00 UTC
Last modified on: 08/09/2023 21:15:00 UTC