Bundler up to 2.2.32 Gemfile argument injection

Summaryinfo

A vulnerability was found in Bundler up to 2.2.32 and classified as critical. This vulnerability affects unknown code of the component Gemfile Handler. Executing a manipulation can lead to argument injection. This vulnerability appears as CVE-2021-43809. The attack may be performed from remote. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Bundler up to 2.2.32. It has been declared as critical. This vulnerability affects an unknown code of the component Gemfile Handler. The manipulation with an unknown input leads to a argument injection vulnerability. The CWE definition for the vulnerability is CWE-88. The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

`Bundler` is a package for managing application dependencies in Ruby. In `bundler` versions before 2.2.33, when working with untrusted and apparently harmless `Gemfile`'s, it is not expected that they lead to execution of external code, unless that's explicit in the ruby code inside the `Gemfile` itself. However, if the `Gemfile` includes `gem` entries that use the `git` option with invalid, but seemingly harmless, values with a leading dash, this can be false. To handle dependencies that come from a Git repository instead of a registry, Bundler uses various commands, such as `git clone`. These commands are being constructed using user input (e.g. the repository URL). When building the commands, Bundler versions before 2.2.33 correctly avoid Command Injection vulnerabilities by passing an array of arguments instead of a command string. However, there is the possibility that a user input starts with a dash (`-`) and is therefore treated as an optional argument instead of a positional one. This can lead to Code Execution because some of the commands have options that can be leveraged to run arbitrary executables. Since this value comes from the `Gemfile` file, it can contain any character, including a leading dash. To exploit this vulnerability, an attacker has to craft a directory containing a `Gemfile` file that declares a dependency that is located in a Git repository. This dependency has to have a Git URL in the form of `-u./payload`. This URL will be used to construct a Git clone command but will be interpreted as the upload-pack argument. Then this directory needs to be shared with the victim, who then needs to run a command that evaluates the Gemfile, such as `bundle lock`, inside. This vulnerability can lead to Arbitrary Code Execution, which could potentially lead to the takeover of the system. However, the exploitability is very low, because it requires a lot of user interaction. Bundler 2.2.33 has patched this problem by inserting `--` as an argument before any positional arguments to those Git commands that were affected by this issue. Regardless of whether users can upgrade or not, they should review any untrustred `Gemfile`'s before running any `bundler` commands that may read them, since they can contain arbitrary ruby code.

The weakness was presented 12/09/2021 as GHSA-fj7f-vq84-fh43. The advisory is shared for download at github.com. This vulnerability was named CVE-2021-43809 since 11/16/2021. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1059.

The vulnerability scanner Nessus provides a plugin with the ID 210115 (SUSE SLED15 / SLES15 / openSUSE 15 Security Update : rubygem-bundler (SUSE-SU-2024:3873-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.2.33 eliminates this vulnerability. Applying the patch 0fad1ccfe9dd7a3c5b82c1496df3c2b4842870d3 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (210115). Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

• Bundler

Version

• 2.2.0
• 2.2.1
• 2.2.2
• 2.2.3
• 2.2.4
• 2.2.5
• 2.2.6
• 2.2.7
• 2.2.8
• 2.2.9
• 2.2.10
• 2.2.11
• 2.2.12
• 2.2.13
• 2.2.14
• 2.2.15
• 2.2.16
• 2.2.17
• 2.2.18
• 2.2.19
• 2.2.20
• 2.2.21
• 2.2.22
• 2.2.23
• 2.2.24
• 2.2.25
• 2.2.26
• 2.2.27
• 2.2.28
• 2.2.29
• 2.2.30
• 2.2.31
• 2.2.32

License

• open-source

CPE 2.3info

• 🔍
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CPE 2.2info

• 🔍
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Once again VulDB remains the best source for vulnerability data.

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