Local Code Execution through Argument Injection via dash leading git url parameter in Gemfile
Summary
| CVE | CVE-2021-43809 |
|---|---|
| State | PUBLISHED |
| Assigner | GitHub_M |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2021-12-08 19:15:10 UTC |
| Updated | 2026-11-02 19:17:45 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 7.3 HIGH from [email protected]
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
EPSS: 0.029090000 probability, percentile 0.869870000 (date 2026-11-02)
Problem Types: CWE-88 | CWE-88 CWE-88: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 7.3 | HIGH | CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H |
| 3.1 | [email protected] | Secondary | 6.7 | MEDIUM | CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H |
| 3.1 | CNA | DECLARED | 6.7 | MEDIUM | CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H |
| 2.0 | [email protected] | Primary | 9.3 | AV:N/AC:M/Au:N/C:C/I:C/A:C |
CVSS v3.1 Breakdown
Attack Vector
LocalAttack Complexity
LowPrivileges Required
LowUser Interaction
RequiredScope
UnchangedConfidentiality
HighIntegrity
HighAvailability
HighCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
CVSS v2.0 Breakdown
Access Vector
NetworkAccess Complexity
MediumAuthentication
NoneConfidentiality
CompleteIntegrity
CompleteAvailability
CompleteAV:N/AC:M/Au:N/C:C/I:C/A:C
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| Local Code Execution through Argument Injection via dash leading git url parameter in Gemfile · Advisory · rubygems/rubygems · GitHub | af854a3a-2127-422b-91ae-364da2661108 | github.com | Exploit, Vendor Advisory |
| Pass "--" to git commands to separate positional and optional args by deivid-rodriguez · Pull Request #5142 · rubygems/rubygems · GitHub | af854a3a-2127-422b-91ae-364da2661108 | github.com | Patch |
| lists.debian.org/debian-lts-announce/2025/05/msg00015.html | af854a3a-2127-422b-91ae-364da2661108 | lists.debian.org | |
| Securing Developer Tools: Package Managers | Sonar | af854a3a-2127-422b-91ae-364da2661108 | www.sonarsource.com | Exploit, Mitigation |
| Changelog for Bundler version 2.2.33 · rubygems/rubygems@0fad1cc · GitHub | af854a3a-2127-422b-91ae-364da2661108 | github.com | Patch |
| Add require parameter to `bundle add`` · rubygems/rubygems@a4f2f8a · GitHub | af854a3a-2127-422b-91ae-364da2661108 | github.com | Patch |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.