Attack Chain

1. An attacker crafts a malicious project configuration file.
2. The attacker leverages a downstream consumer application that utilizes yeoman-environment and passes the attacker-controlled project configuration to it.
3. The installLocalGenerators() function within yeoman-environment is triggered.
4. Due to the vulnerability, the repository.install() method is called without user confirmation, using package names supplied in the malicious configuration.
5. The attacker-specified packages are downloaded and installed from the npm registry (or a malicious mirror).
6. The installed packages execute arbitrary code during the CLI bootstrap, potentially granting the attacker control over the system.
7. The attacker establishes persistence through scheduled tasks or startup scripts.
8. The attacker performs lateral movement within the network to compromise additional systems.

Impact

Successful exploitation of this vulnerability allows an attacker to achieve arbitrary code execution on systems using vulnerable versions of yeoman-environment. This can lead to complete system compromise, data theft, and further propagation of the attack within the network. The severity is high due to the potential for remote code execution without user interaction.

Recommendation

• Upgrade yeoman-environment to version 6.0.1 or later to incorporate the fix that adds an interactive confirmation prompt before installation.
• Deploy the Sigma rules provided below to detect attempts to exploit CVE-2026-42089 by monitoring for suspicious npm package installations via CLI.
• Implement input validation and sanitization on project configuration files to prevent attackers from injecting malicious package names.
• Monitor process creation events for unusual or unexpected processes spawned by npm or node.