Code Injection in Vim via Cucumber Filetype Plugin

Executive Summary

This vulnerability is a code injection issue in the cucumber filetype plugin of Vim versions prior to 9.2.0496 when Vim is built with +ruby support.

Specifically, the s:stepmatch() function processes step-definition patterns from .rb files in cucumber repositories by embedding them into a Ruby Kernel.eval argument without proper escaping.

An attacker can craft a malicious regex pattern in a step-definition file that, when matched during a step-jump operation (triggered by [d or ]d mappings), executes arbitrary Ruby code and shell commands with the privileges of the user running Vim.

The vulnerability requires the victim to open a cucumber-style repository containing the attacker-controlled file and invoke the step-jump mapping on a matching feature line.

This issue was fixed in Vim patch version 9.2.0496 by replacing Kernel.eval() with Regexp.new(), preventing code injection.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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Impact Analysis

If exploited, this vulnerability allows an attacker to execute arbitrary Ruby code and shell commands on your system with the same privileges as the user running Vim.

This can lead to unauthorized command execution, potentially compromising your system's security and integrity.

However, exploitation requires specific conditions: you must open a cucumber-style repository containing a malicious step-definition file and invoke the step-jump mapping on a matching feature line.

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Detection Guidance

This vulnerability can be detected by checking if your Vim installation is a version prior to 9.2.0496 and if it is compiled with +ruby support. Additionally, detection involves verifying if the cucumber filetype plugin is in use and if any cucumber-style repositories with .rb step-definition files are opened.

There are no specific network detection commands since exploitation requires local interaction with Vim and a crafted repository. However, you can check your Vim version and ruby support with the following commands:

• vim --version | grep "+ruby" # Checks if Vim is compiled with ruby support
• vim --version | head -n 1 # Checks Vim version

If the version is earlier than 9.2.0496 and +ruby support is enabled, your system is vulnerable.

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Mitigation Strategies

The immediate mitigation step is to upgrade Vim to version 9.2.0496 or later, where the vulnerability has been patched.

If upgrading is not immediately possible, avoid opening cucumber-style repositories containing untrusted .rb step-definition files and refrain from using the step-jump mappings ([d or ]d) in such repositories.

Additionally, consider disabling the cucumber filetype plugin or compiling Vim without +ruby support if those features are not required.

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