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…

PriorityP339high7.3CVSS 3.1

AVLACLPRLUIRSUCHIHAH

EPSS

2.80%

84.8th percentile

`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

Affected

8 ranges

Vendor	Product	Version range	Fixed in
bundler	bundler	< 2.2.33	2.2.33
bundler	bundler	>= 0 < 2.2.33	2.2.33
debian	rubygems	< rubygems 3.3.5-1 (bookworm)	rubygems 3.3.5-1 (bookworm)
rubygems	rubygems	< 2.2.33	2.2.33
rubygems	rubygems	>= 0 < 3.2.5-2+deb11u1	3.2.5-2+deb11u1
rubygems	rubygems	>= 0 < 3.3.5-1	3.3.5-1
rubygems	rubygems	>= 0 < 3.3.5-1	3.3.5-1
rubygems	rubygems	>= 0 < 3.3.5-1	3.3.5-1

CVSS provenance

nvdv3.17.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

nvdv2.09.3CRITICALAV:N/AC:M/Au:N/C:C/I:C/A:C

osv7.3HIGH

vendor_debian6.7MEDIUM

vendor_redhat6.7MEDIUM

Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.