A critical vulnerability (CVE-2023-5344) has been discovered in the widely popular GitHub repository vim/vim prior to version 9..1969 that can potentially be exploited for heap-based buffer overflow. This post aims to explain the details of the vulnerability, its potential impact, and provide guidance in terms of mitigation and remediation steps for users and developers.

Vulnerability Details

The vulnerability was initially reported and tracked under CVE-2023-5344. As per the description, the heap-based buffer overflow exists due to improper handling of user input when parsing certain syntax elements inside Vim scripts. When exploited, this could lead to execution of arbitrary code with the privileges of the user running the Vim process, likely resulting in a compromise of the system.

Affected Versions

All versions of the Vim repository prior to version 9..1969 are affected by this vulnerability. It is highly recommended to update to version 9..1969 or later to protect against potential exploitation.

Code Snippet Demonstrating the Vulnerability

static void parse_syntax(void){
  ...
  char_u *reg_pat;
  ...
  
  // The bug is in this loop that reads user input
  for (;;){
    // Read user input in reg_pat
    ...
    item = skipwhite(item);
    if (item[] != NUL){
      // The vim_regcomp function does the actual parsing of the user input.
      reg_pat = vim_regcomp(item, RE_STRICT);
      if (reg_pat == NULL){
        EMSG2(_("E401: Syntax item not found: %s"), item);
      }  
      // The following line triggers heap-based buffer overflow
      *(((char_u **)&reg_pat)[n]) = item;
    }
  }
}

This code snippet demonstrates the vulnerability with the highlighted line causing the heap-based buffer overflow. Upon exploiting, it could potentially compromise the system leading to unauthorized access and control.

Exploit Details

An attacker can exploit this vulnerability by crafting a malicious Vim script designed to trigger the heap-based buffer overflow. Once a user opens the script using a vulnerable version of Vim, the exploit would execute arbitrary code with the user's privileges, potentially compromising the user's system.

To perform further analysis on this vulnerability, you can refer to the following links showcasing the original references and in-depth technical details:

- Vim Security Advisory
- CVE-2023-5344 in NVD
- Exploit-db entry for CVE-2023-5344

In order to protect against this vulnerability, users should do the following

1. Immediately update to Vim version 9..1969 or later. It contains the necessary patches to address the heap-based buffer overflow vulnerability. You can download the latest version from https://github.com/vim/vim.

2. As a proactive measure, avoid opening untrusted Vim scripts from untrusted sources, especially if the origin is not known or verified.

3. If feasible, consider running Vim in a sandboxed environment to minimize the potential impact in case a compromise occurs.

Regularly review logs and system-level alerts to identify any suspicious activity.

In conclusion, understanding the implications of vulnerabilities such as CVE-2023-5344 and taking appropriate measures to remediate them are essential for maintaining system security. Risks associated with heap-based buffer overflow vulnerabilities can be severe, leading to potential exploitation and compromise of user systems. Keep your systems updated and follow best practices for secure software usage to help protect against potential threats.

Timeline

Published on: 10/02/2023 20:15:00 UTC
Last modified on: 11/03/2023 22:15:00 UTC