CVE-2022-2175 is a recently discovered security vulnerability in the widely-used text editor Vim (Vi IMproved), affecting versions prior to 8.2. Specifically, this vulnerability is related to a buffer over-read, which could potentially allow an attacker to access memory contents that should have been inaccessible otherwise.

In this blog post, we will dive deep into the details of this vulnerability, exploring the relevant code snippets, links to the original references, and exploit details. Our aim is to give you a better understanding of the issue and a broader perspective on how to protect your systems from similar vulnerabilities.

Code Snippet

The buffer over-read vulnerability lies in the src/regexp_nfa.c file of the Vim source code, specifically in the nfa_regatom() function:

static int
nfa_regatom()
{
    ...
    if (reg_string_start != NULL && *reg_string_start != NUL)
        ret = nfa_reg_str();
    else
    {
        c = getchr();
        switch (c)
        {
            ...
        }
    }
    ...
}

The issue resides in the handling of the reg_string_start variable, which is used to point to the start of a regular expression subpattern. If this variable is not properly set or if its value is outside the boundaries of the active buffer, the nfa_reg_str() function may access memory that is outside the bounds of the intended target data, leading to a buffer over-read.

For a detailed description of the vulnerability, the official CVE entry and the GitHub security advisory can be found at the following links:

* CVE Entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-2175
* GitHub Security Advisory: https://github.com/vim/vim/security/advisories/GHSA-p2cq-44w6-39qv

To patch the vulnerability, you can refer to the official commit that resolves the issue in the Vim GitHub repository:

* Patch Commit: https://github.com/vim/vim/commit/877f926cd659aea6dd42e95c181b032f8387c7cb

Exploit Details

To exploit this vulnerability, an attacker could craft a carefully designed regular expression pattern that triggers the buffer over-read in Vim's regular expression engine. This could potentially expose sensitive information, such as passwords or other confidential data, that was stored in the affected memory region.

Given the right circumstances, this flaw could lead to information leaks or even remote code execution. However, creating a practical exploit would likely require a deep understanding of both Vim's internal memory management and the host system's runtime environment.

Conclusion

CVE-2022-2175 is a notable vulnerability, as it not only highlights the risks associated with the popular Vim text editor but also serves as a reminder of the importance of proper memory management in software development.

To avoid similar issues in the future, it is crucial to carefully validate user input data, implement robust bounds checking, and apply security best practices when developing and maintaining software.

As always, it's essential to keep your software up-to-date and apply security patches promptly. In the case of Vim, make sure to update to version 8.2 or later to protect your systems from this vulnerability.

Timeline

Published on: 06/23/2022 13:15:00 UTC
Last modified on: 08/26/2022 19:16:00 UTC