Recently, a critical vulnerability (CVE-2022-1771) was discovered in the GitHub repository of Vim, the popular text editor, which can lead to a Denial of Service (DoS) condition. This vulnerability has been identified to be a type of "Uncontrolled Recursion," a programming error that can have profound implications for the software being exploited. This blog post will take a detailed look at the vulnerability, the code snippet that's causing the issue, the original references related to error discovery, and some exploit details.


Vim is a widely-used text editor, highly popular among programmers and system administrators due to its highly customizable interface and availability on various platforms. However, no software is immune to vulnerabilities, and CVE-2022-1771 proves just that. This vulnerability has been found in Vim versions prior to 8.2.4975. It involves an error in recursive function calls within Vim, leading to uncontrolled recursion that can cause a severe impact on the software performance and potentially crash the system.

The Code Snippet

The vulnerable code snippet has been identified in the GitHub repository vim/vim. For more details, you can refer to the original commit that fixed the issue:


The problematic code can be found in the file "charset.c"

utf_ptr2cells(const char_u *p)
    int c;

    if (*p >= x80) {
	c = utf_ptr2char(p);
	// avoid the "default:" label in 'utf_char2cells()' to avoid a
	// warning for not all enum values being used
	if (c >= 256)
	    return utf_char2cells(c);
    return 1 + (char2cells(*p) == 2);

This code snippet contains the recursive function call to 'char2cells,' which ultimately leads to uncontrolled recursion. When this code is executed, the utf_ptr2cells function can cause a stack overflow, leading to a Denial of Service (DoS) condition.

Original References

Here are some original references that will guide you to understand the vulnerability more thoroughly:

1. The National Vulnerability Database (NVD) entry for CVE-2022-1771:
2. The GitHub commit that fixed the vulnerability:

Exploit Details

Now that you understand the issue let's delve into the details of exploiting the vulnerability. To exploit this vulnerability, an attacker would need to craft a specially designed file that triggers the uncontrolled recursion in the vulnerable code snippet mentioned above. When a user opens this malicious file using a vulnerable Vim version, the uncontrolled recursion will lead to a stack overflow, causing the program to crash and result in a Denial of Service (DoS) condition.

To protect their systems from this vulnerability, users are advised to update Vim to version 8.2.4975 or later. This update can be found at:



CVE-2022-1771, an uncontrolled recursion vulnerability in Vim's GitHub repository, can cause significant damage, as it may lead to a Denial of Service (DoS) condition. By understanding the code snippet responsible for the error, referring to the original references, and knowing exploit details, you can better protect your Vim installations. Ensure that you always maintain software updates and patches to stay protected from emerging vulnerabilities that may put your systems at risk.


Published on: 05/18/2022 20:15:00 UTC
Last modified on: 08/26/2022 19:14:00 UTC