7.3
HIGH
CVE-2021-43809
"Bundler Git Command Injection Vulnerability"
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.

INFO

Published Date :

Dec. 8, 2021, 7:15 p.m.

Last Modified :

Nov. 16, 2023, 3:04 a.m.

Remotely Exploitable :

No

Impact Score :

5.9

Exploitability Score :

1.3
Affected Products

The following products are affected by CVE-2021-43809 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Bundler bundler
References to Advisories, Solutions, and Tools

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2021-43809 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2021-43809 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by [email protected]

    May. 14, 2024

    Action Type Old Value New Value
  • Reanalysis by [email protected]

    Nov. 16, 2023

    Action Type Old Value New Value
    Changed Reference Type https://github.com/rubygems/rubygems/commit/0fad1ccfe9dd7a3c5b82c1496df3c2b4842870d3 Patch, Third Party Advisory https://github.com/rubygems/rubygems/commit/0fad1ccfe9dd7a3c5b82c1496df3c2b4842870d3 Patch
    Changed Reference Type https://github.com/rubygems/rubygems/commit/a4f2f8ac17e6ce81c689527a8b6f14381060d95f Patch, Third Party Advisory https://github.com/rubygems/rubygems/commit/a4f2f8ac17e6ce81c689527a8b6f14381060d95f Patch
    Changed Reference Type https://github.com/rubygems/rubygems/pull/5142 Patch, Third Party Advisory https://github.com/rubygems/rubygems/pull/5142 Patch
    Changed Reference Type https://github.com/rubygems/rubygems/security/advisories/GHSA-fj7f-vq84-fh43 Exploit, Third Party Advisory https://github.com/rubygems/rubygems/security/advisories/GHSA-fj7f-vq84-fh43 Exploit, Vendor Advisory
    Changed Reference Type https://www.sonarsource.com/blog/securing-developer-tools-package-managers/ Exploit, Mitigation, Third Party Advisory https://www.sonarsource.com/blog/securing-developer-tools-package-managers/ Exploit, Mitigation
  • Modified Analysis by [email protected]

    Oct. 27, 2023

    Action Type Old Value New Value
    Changed Reference Type https://www.sonarsource.com/blog/securing-developer-tools-package-managers/ No Types Assigned https://www.sonarsource.com/blog/securing-developer-tools-package-managers/ Exploit, Mitigation, Third Party Advisory
    Added CWE NIST CWE-88
  • CVE Modified by [email protected]

    Oct. 25, 2023

    Action Type Old Value New Value
    Changed 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. `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.
    Added Reference https://www.sonarsource.com/blog/securing-developer-tools-package-managers/ [No Types Assigned]
  • Initial Analysis by [email protected]

    Dec. 13, 2021

    Action Type Old Value New Value
    Added CVSS V2 Metadata Victim must voluntarily interact with attack mechanism
    Added CVSS V2 NIST (AV:N/AC:M/Au:N/C:C/I:C/A:C)
    Added CVSS V3.1 NIST AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
    Changed Reference Type https://github.com/rubygems/rubygems/commit/0fad1ccfe9dd7a3c5b82c1496df3c2b4842870d3 No Types Assigned https://github.com/rubygems/rubygems/commit/0fad1ccfe9dd7a3c5b82c1496df3c2b4842870d3 Patch, Third Party Advisory
    Changed Reference Type https://github.com/rubygems/rubygems/commit/a4f2f8ac17e6ce81c689527a8b6f14381060d95f No Types Assigned https://github.com/rubygems/rubygems/commit/a4f2f8ac17e6ce81c689527a8b6f14381060d95f Patch, Third Party Advisory
    Changed Reference Type https://github.com/rubygems/rubygems/pull/5142 No Types Assigned https://github.com/rubygems/rubygems/pull/5142 Patch, Third Party Advisory
    Changed Reference Type https://github.com/rubygems/rubygems/security/advisories/GHSA-fj7f-vq84-fh43 No Types Assigned https://github.com/rubygems/rubygems/security/advisories/GHSA-fj7f-vq84-fh43 Exploit, Third Party Advisory
    Added CPE Configuration OR *cpe:2.3:a:bundler:bundler:*:*:*:*:*:ruby:*:* versions up to (excluding) 2.2.33
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2021-43809 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Exploit Prediction

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.

0.12 }} 0.02%

score

0.44692

percentile

CVSS31 - Vulnerability Scoring System
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality
Integrity
Availability