Yikes! A new vulnerability ID CVE-2023-36272 has been registered, and it's related to a heap buffer overflow that has been discovered in LibreDWG v.12.5. In this long read, we'll dive into the specifics of this vulnerability, understand the code snippet that exposes the flaw, explore the links to original references, and outline essential details about the exploit that you should know.

To give an overview, LibreDWG is an open-source library for reading and writing DWG files, the primary binary file format for CAD. The vulnerability lies in the function bit_utf8_to_TU as present in the bits.c file. This function, when triggered, can lead to serious consequences like remote code execution, crashes, or information leaks in applications using the LibreDWG library.

Code Snippet

The vulnerable part of the code can be found in the src/bits.c file in the bit_utf8_to_TU() function:

char16_t *
bit_utf8_to_TU (bitset *restrict set, const char *restrict text, int *size)
  // ...
  // code for handling the UTF8 to TU conversion

  while (src < len)
      if (!(ctrl = (*src & xC)))
          *dst++ = *src++; // vulnerability here!
      // ...
      // code handling other cases

Vulnerability Explanation

As seen in the code snippet, an improperly validated control code (CTRL) may lead to an insecure copying of arbitrary data from src to dst. This means, if a malicious input is provided, the heap buffer in the dst variable could overflow, giving an attacker a chance to execute arbitrary code or perform a Denial of Service (DoS) attack using a crafted DWG file.

The problem occurs because the src pointer advances without proper validation checks and continues to copy data to dst, without verifying if there's enough buffer space available in dst.

Exploit Details

A well-crafted DWG file carrying malicious content can be used to trigger this vulnerability. An attacker can exploit this by performing the following steps:

1. Create a specially crafted DWG file that contains unicode control characters aimed at triggering the vulnerable code block in bit_utf8_to_TU.

2. Load the crafted DWG file into vulnerable software relying on LibreDWG v.12.5 to read and parse DWG content.

3. Watch the buffer overflow vulnerability take effect; it could potentially crash the application, leak sensitive information, or even allow the attacker to remote execute code by overwriting adjacent heap-memory structures with malicious payloads.

Original References

1. Original CVE report for CVE-2023-36272

2. LibreDWG GitHub repository

3. LibreDWG official documentation

How to Protect Yourself

The best way to protect yourself from this vulnerability is to upgrade the LibreDWG library to its latest versions, or at least beyond v.12.5. Keep an eye on LibreDWG's GitHub page and their official website for any updates, patches, and developments related to this vulnerability.

In conclusion, the CVE-2023-36272 vulnerability in the LibreDWG v.12.5 library can cause significant security concerns if left unaddressed. Make sure to keep all software up-to-date and stay informed about vulnerabilities to maintain secure environments.


Published on: 06/23/2023 15:15:00 UTC
Last modified on: 06/27/2023 12:18:00 UTC