Vim is a powerful and versatile open-source command line text editor that is highly popular among programmers, sysadmins, and other tech-savvy users. It recently came to light that a particular vulnerability, tagged by the CVE identifier CVE-2023-48234, could potentially expose mere users of Vim to an overflow bug for large counts given while getting the count for a normal mode z command. In this post, we will delve into the details of this vulnerability, discuss the impact and mitigation measures, and provide resources for further information.

Vulnerability Details

During the process of getting the count for a normal mode z command in Vim, there is a possibility that it may overflow if the count given is exceptionally large. The precise code snippet in question is as follows:

void get_normal_mode_z_command_count(void)
  long count = ;
  while (vim_isdigit(gchar_cursor()))
    count = count * 10 + (gchar_cursor() - '');
  if (count <= )
    count = 1;
  //... other code here ...

Now, while this vulnerability is present, it is crucial to understand that the impact of this issue is relatively low. This is primarily because user interaction is required, and even then, a crash may not happen in all situations.

Original References

For an in-depth understanding of this vulnerability, and to review the original findings, please consult the following links:

1. Vim's Official GitHub Repository
2. Vim's Normal Mode Vulnerability Discussion
3. CVE-2023-48234 Top Level Entry

Mitigation and Recommendations

Fortunately, the maintainers of Vim have already released a patch that addresses this issue in commit 58f9befca1. This patch has also been integrated into the latest release version of Vim, 9..2109. As a result, it is highly advised that users upgrade their Vim installations to this latest version as soon as possible.

Unfortunately, there are no known workarounds for those who cannot upgrade at the moment. If you cannot upgrade your version of Vim, it is advised to monitor the situation closely and exercise caution while working with large counts in normal mode z commands.


In conclusion, while CVE-2023-48234 does represent a genuine vulnerability in Vim, its overall impact is limited. By upgrading to the latest release version of Vim, 9..2109, you can quickly and effectively eliminate the risks associated with this vulnerability. It is always advised to keep your software up to date and subscribe to security notifications to remain informed of any potential threats or vulnerabilities. Stay safe, and happy coding!


Published on: 11/16/2023 23:15:09 UTC
Last modified on: 01/25/2024 21:33:46 UTC