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HIGH

CVE-2021-43809

CVSS v3

7.3

HIGH

EPSS Score

2.9 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • bundlerRubyGemsall versions · fixed in 2.2.33
  • rubyAlmaLinux:8all versions · fixed in 2.5.9-114.module_el8.10.0+3991+5e651d4eand 4 other packages
  • rubygem-abrtAlmaLinux:8all versions · fixed in 0.3.0-4.module_el8.5.0+2625+ec418553
  • rubygem-abrt-docAlmaLinux:8all versions · fixed in 0.3.0-4.module_el8.10.0+3871+342e2c2f
  • rubygem-bigdecimalAlmaLinux:8all versions · fixed in 1.3.4-114.module_el8.10.0+3991+5e651d4e
  • rubygem-bsonAlmaLinux:8all versions · fixed in 4.3.0-2.module_el8.5.0+259+8cec6917
  • rubygem-bson-docAlmaLinux:8all versions · fixed in 4.3.0-2.module_el8.5.0+2625+ec418553
  • rubygem-bundlerAlmaLinux:8all versions · fixed in 1.16.1-5.module_el8.10.0+3991+5e651d4eand 1 other package

17 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-43809 Red Hat Product Security144 products fixed · 50 known affected

    rubygem-bundler: unexpected code execution in Gemfiles

    rubygem-bundler as a component of Red Hat Enterprise Linux 7 · rubygem-bundler-doc as a component of Red Hat Enterprise Linux 7 · rubygem-bundler.src as a component of Red Hat Enterprise Linux 7

  • RHSA-2025:7539 Red Hat Product Security144 products fixed

    Red Hat Security Advisory: ruby:2.5 security update

Full record on NVD

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 befo

Technical details

Published
2021-12-08

Frequently asked questions

What is CVE-2021-43809?

`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 befo

Is CVE-2021-43809 actively exploited?

Active exploitation of CVE-2021-43809 has not been confirmed. Its EPSS score was 2.9% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-43809?

CVE-2021-43809 has a CVSS v3 base score of 7.3 (HIGH severity).

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