CVE-2024-53899: Virtualenv Command Injection Vulnerability

CVE-2024-53899 Overview

CVE-2024-53899 is a command injection vulnerability affecting virtualenv versions prior to 20.26.6. The vulnerability exists in the activation scripts for virtual environments, where magic template strings are not properly quoted during replacement operations. This improper quoting allows attackers with local access to inject arbitrary commands that execute when a user activates the compromised virtual environment.

Critical Impact

Attackers with local access can achieve arbitrary command execution with the privileges of the user activating the virtual environment, potentially leading to complete system compromise, credential theft, or lateral movement within development environments.

Affected Products

• virtualenv versions prior to 20.26.6

Discovery Timeline

• 2024-11-24 - CVE-2024-53899 published to NVD
• 2025-02-10 - Last updated in NVD database

Technical Details for CVE-2024-53899

Vulnerability Analysis

This command injection vulnerability (CWE-77, CWE-78) affects the activation script generation mechanism in virtualenv. When virtualenv creates activation scripts for virtual environments, it uses template strings that contain placeholders for environment-specific values. These template strings are replaced with actual values during the generation process. However, the replacement values are not properly quoted or sanitized, creating an injection point.

An attacker who can influence the values used in these template replacements can inject shell metacharacters and arbitrary commands into the generated activation scripts. When a legitimate user subsequently activates the virtual environment, the injected commands execute with that user's privileges.

The attack requires local access, making it particularly dangerous in shared development environments, CI/CD pipelines, or scenarios where virtual environments are created from untrusted sources. Note that this vulnerability is distinct from CVE-2024-9287, which addresses a different security issue.

Root Cause

The root cause is improper neutralization of special elements used in command strings. The virtualenv activation script generator fails to properly escape or quote the values substituted into magic template strings. This allows shell metacharacters present in the replacement values to be interpreted as command syntax rather than literal data when the activation script is sourced by a shell.

Attack Vector

The vulnerability requires local access (AV:L) and exploitation depends on the attacker's ability to control or influence values that are substituted into the activation script templates. Attack scenarios include:

• Creating a malicious virtual environment with crafted directory names or configuration values containing shell metacharacters
• Distributing compromised virtual environment configurations through shared repositories
• Exploiting automated build systems that process untrusted virtual environment specifications

When a user runs the activation script (e.g., source venv/bin/activate), the injected commands execute in the user's shell context. The vulnerability requires low privileges to exploit and no user interaction beyond normal virtual environment activation.

Detection Methods for CVE-2024-53899

Indicators of Compromise

• Activation scripts (activate, activate.csh, activate.fish, etc.) containing unexpected shell commands or suspicious character sequences
• Virtual environment directories with unusual names containing shell metacharacters like backticks, $(), semicolons, or pipe characters
• Unexpected process spawning when activating virtual environments
• Anomalous network connections or file system modifications occurring during environment activation

Detection Strategies

• Audit activation scripts within virtual environments for the presence of command injection patterns such as command substitution syntax, semicolons, or pipe operators in unexpected locations
• Monitor process execution chains for suspicious child processes spawned by shell interpreters during virtual environment activation
• Implement file integrity monitoring on activation scripts in production and CI/CD virtual environments
• Scan virtual environment configurations and directory structures for special characters that could be used for injection

Monitoring Recommendations

• Enable shell command logging (e.g., bash history, auditd) to capture commands executed during virtual environment activation
• Deploy endpoint detection to alert on unusual process trees originating from activation script execution
• Monitor for virtual environments created with non-standard directory paths or configuration values
• Implement continuous security scanning of development and build environments for vulnerable virtualenv versions

How to Mitigate CVE-2024-53899

Immediate Actions Required

• Upgrade virtualenv to version 20.26.6 or later immediately across all development environments, CI/CD systems, and production deployments
• Audit existing virtual environments for potentially compromised activation scripts
• Regenerate activation scripts for critical virtual environments using the patched version
• Review virtual environments sourced from external or untrusted repositories before use

Patch Information

The fix is available in virtualenv version 20.26.6, released by the maintainers. The patch properly quotes magic template string replacements to prevent command injection. Detailed information about the fix can be found in the GitHub Pull Request #2771 and the GitHub Release 20.26.6.

Workarounds

• Manually inspect and sanitize activation scripts before sourcing them, particularly for virtual environments from untrusted sources
• Restrict virtual environment creation to trusted paths without special characters
• Implement directory name restrictions in build pipelines to prevent shell metacharacters in virtual environment paths
• Use containerization to isolate virtual environment activation and limit the blast radius of potential exploitation

# Upgrade virtualenv to the patched version
pip install --upgrade virtualenv>=20.26.6

# Verify installed version
virtualenv --version

# Regenerate activation scripts for existing virtual environments
virtualenv --clear /path/to/existing/venv