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CVE-2021-43809

Description

`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.

Priority: HIGH
CVSS v3: 7.3
Component: bundler
Publish Date: Dec 8, 2021
Related ID: --
CVSS v2: HIGH
Modified Date: Dec 8, 2021

Find out more about CVE-2021-43809 from the MITRE-CVE dictionary and NIST NVD


Products Affected

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Product Name Status Defect Fixed Downloads
Linux
Wind River Linux LTS 17 Won't Fix -- -- --
Wind River Linux 8 Requires LTSS -- -- --
Wind River Linux 9 Requires LTSS -- -- --
Wind River Linux 7 Requires LTSS -- -- --
Wind River Linux LTS 21 Won't Fix -- -- --
Wind River Linux LTS 18 Won't Fix -- -- --
Wind River Linux LTS 19 Won't Fix -- -- --
Wind River Linux CD release Won't Fix -- -- --
VxWorks
VxWorks 7 Not Vulnerable -- -- --
VxWorks 6.9 Not Vulnerable -- -- --

Related Products

Product Name Status Defect Fixed Downloads

Notes
Requires LTSS - customers must have active LTSS (Long Term Security Shield) Support to receive up-to-date information about vulnerabilities that may affect legacy software. Please contact your Wind River account team or see https://docs.windriver.com/bundle/Support_and_Maintenance_Supplemental_Terms_and_Conditions and https://support2.windriver.com/index.php?page=plc for more information.
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