CVE-2021-43809 : Exploit Details and Defense Strategies

Bundler is a package for managing application dependencies in Ruby. In

bundler

versions before 2.2.33, a vulnerability exists that allows for Local Code Execution through Argument Injection via leading dashes in the git URL parameter in Gemfile.

Understanding CVE-2021-43809

What is CVE-2021-43809?

In Bundler versions before 2.2.33, a vulnerability in handling Git URLs in Gemfile could lead to malicious code execution due to the mishandling of optional arguments that start with a dash.

The Impact of CVE-2021-43809

This vulnerability can result in arbitrary code execution, potentially leading to a system takeover. However, its exploitability is low as it requires significant user interaction to leverage.

Technical Details of CVE-2021-43809

Vulnerability Description

The vulnerability arises from mishandling Git URLs in Gemfile that start with a dash, leading to command injection and potential code execution.

Affected Systems and Versions

Vendor: RubyGems
Product: RubyGems
Versions Affected: < 2.2.33

Exploitation Mechanism

Craft a directory with a Gemfile containing a Git URL of

-u./payload

Share the directory with the victim, who runs a Bundler command like

bundle lock

Arbitrary code execution is possible due to mishandling of Git commands with leading dashes.

Mitigation and Prevention

Immediate Steps to Take

Upgrade to Bundler version 2.2.33
Review all Gemfile dependencies before executing any Bundler commands

Long-Term Security Practices

Regularly update dependencies and packages
Conduct security audits on code repositories

Patching and Updates

Bundler 2.2.33 has patched this issue by adding

--

as an argument to affected Git commands to prevent command injection.