CVE-2020-7666 in u-root
Summary
by MITRE
This affects all versions of package github.com/u-root/u-root/pkg/cpio. It is vulnerable to leading, non-leading relative path traversal attacks and symlink based (relative and absolute) path traversal attacks in cpio file extraction.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/12/2020
The vulnerability identified as CVE-2020-7666 resides within the github.com/u-root/u-root/pkg/cpio package, which is a critical component in Unix-like operating systems for handling cpio archive files. This package serves as a fundamental tool for extracting and creating cpio archives, making it widely used across various system administration and deployment scenarios. The flaw manifests in how the package processes file paths during extraction operations, creating a significant security risk that affects all versions of the software. The vulnerability specifically targets the path handling mechanisms within the cpio extraction process, allowing attackers to manipulate the extraction behavior through carefully crafted archive contents.
The technical implementation of this vulnerability stems from inadequate validation of file paths during cpio archive extraction. Attackers can exploit this weakness by creating malicious cpio archives containing specially constructed file paths that bypass normal security checks. The vulnerability encompasses multiple attack vectors including leading relative path traversal, non-leading relative path traversal, and symlink-based path traversal attacks. These attack methods allow adversaries to manipulate the extraction destination of files, potentially causing arbitrary file writes to locations outside the intended target directory. The issue is particularly dangerous because it operates at the archive extraction level, meaning that any application or system utilizing this package for cpio processing becomes vulnerable to these attacks.
The operational impact of CVE-2020-7666 extends beyond simple path traversal concerns, as it can enable attackers to compromise system integrity and potentially escalate privileges. When exploited, this vulnerability allows attackers to write files to arbitrary locations on the filesystem, which could include system directories, configuration files, or sensitive data locations. The attack surface is broad since the u-root package is used in various contexts including embedded systems, container environments, and system recovery tools. This makes the vulnerability particularly concerning for environments where cpio archives are processed without proper security controls, such as automated deployment systems, build pipelines, or system recovery utilities that may encounter untrusted archive content.
Mitigation strategies for this vulnerability require immediate attention from system administrators and developers who utilize the affected package. The primary recommendation involves updating to a patched version of the u-root package where the path traversal vulnerabilities have been addressed through proper input validation and path sanitization. Organizations should implement strict file path validation mechanisms that reject or normalize any suspicious path components during archive extraction operations. Additionally, security practices should include running extraction processes with minimal privileges, implementing proper sandboxing techniques, and ensuring that cpio archives are processed only from trusted sources. This vulnerability aligns with CWE-22, which specifically addresses path traversal flaws, and represents a clear violation of the principle of least privilege in security design. The ATT&CK framework categorizes this as a path traversal technique that can be leveraged for privilege escalation and arbitrary file write operations, making it a significant concern for defensive security teams.