CVE-2019-16776 Explained : Impact and Mitigation

Any version of the npm CLI that is older than 6.13.3 has a vulnerability that allows for Arbitrary File Write. It does not effectively block access to folders beyond the designated node_modules folder via the bin field. If the package.json bin field is configured correctly, a package publisher can manipulate and/or gain access to arbitrary files on a user's system when the package is installed. This exploit can still occur through install scripts, even if the user tries to prevent it by using the --ignore-scripts install option.

Understanding CVE-2019-16776

Versions of the npm CLI prior to 6.13.3 are vulnerable to an Arbitrary File Write. It fails to prevent access to folders outside of the intended node_modules folder through the bin field. A properly constructed entry in the package.json bin field would allow a package publisher to modify and/or gain access to arbitrary files on a user's system when the package is installed. This behavior is still possible through install scripts. This vulnerability bypasses a user using the --ignore-scripts install option.

What is CVE-2019-16776?

CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

The Impact of CVE-2019-16776

CVSS Score: 7.7 (High)
Attack Vector: Network
Attack Complexity: High
Privileges Required: Low
User Interaction: Required
Scope: Changed
Confidentiality Impact: High
Integrity Impact: High
Availability Impact: None

Technical Details of CVE-2019-16776

Vulnerability Description

The vulnerability in npm CLI versions prior to 6.13.3 allows for Arbitrary File Write, enabling unauthorized access to files outside the intended directory.

Affected Systems and Versions

Product: cli
Vendor: npm
Versions Affected: < 6.13.3

Exploitation Mechanism

The vulnerability can be exploited by manipulating the package.json bin field to gain access to arbitrary files during package installation, bypassing user protections.

Mitigation and Prevention

Immediate Steps to Take

Update npm CLI to version 6.13.3 or newer to mitigate the vulnerability.
Avoid installing packages from untrusted sources.
Monitor for any unauthorized file modifications on the system.

Long-Term Security Practices

Regularly update software and dependencies to patch known vulnerabilities.
Implement proper access controls and permissions to restrict file access.

Patching and Updates

Stay informed about security advisories and promptly apply patches released by npm and other relevant vendors.