CVE-2020-7669 in u-root
Summary
by MITRE
This affects all versions of package github.com/u-root/u-root/pkg/tarutil. It is vulnerable to both leading and non-leading relative path traversal attacks in tar file extraction.
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Analysis
by VulDB Data Team • 11/12/2020
The vulnerability identified as CVE-2020-7669 resides within the github.com/u-root/u-root/pkg/tarutil package, a critical component used for tar file extraction operations in various systems. This issue represents a path traversal vulnerability that affects all versions of the affected package, making it a persistent security risk across multiple deployments. The vulnerability specifically targets the tar file extraction functionality where improper handling of file paths allows attackers to manipulate the extraction process to write files outside of the intended target directory.
The technical flaw manifests through two distinct types of relative path traversal attacks that exploit how the tarutil package processes file paths during extraction. The leading relative path traversal occurs when tar archives contain entries that begin with ../ sequences, while the non-leading relative path traversal involves paths that contain ../ components not at the beginning but within the file path structure. Both attack vectors enable an attacker to manipulate the extraction destination, potentially overwriting critical system files or creating malicious files in unauthorized locations. This vulnerability operates at the file system level where the extraction process fails to properly validate or sanitize the paths contained within tar archives before writing files to disk.
The operational impact of CVE-2020-7669 extends beyond simple file system manipulation, creating potential for more severe security consequences. An attacker could leverage this vulnerability to overwrite system binaries, configuration files, or create backdoor files that persist across system reboots. The attack surface is particularly concerning in environments where untrusted tar archives are processed, such as container image handling, automated build systems, or any application that extracts tar files without proper path validation. This vulnerability aligns with CWE-22, which specifically addresses path traversal flaws in software systems, and represents a direct threat to the principle of least privilege and system integrity. The vulnerability can be exploited through various attack vectors including supply chain compromises where malicious tar archives are introduced during software distribution or through direct attack on systems that process user-provided tar files.
Mitigation strategies for CVE-2020-7669 should focus on immediate remediation through package updates to versions that address the path traversal vulnerability. Organizations must implement comprehensive input validation for all tar file processing operations, ensuring that file paths are properly sanitized before extraction occurs. The implementation of strict path validation mechanisms that reject any path components containing ../ sequences or that attempt to traverse above the intended extraction directory provides a robust defense against both leading and non-leading relative path traversal attacks. Additionally, systems should employ sandboxing techniques during tar extraction operations, limiting the scope of file system access to only the intended directories. From an operational security perspective, regular security audits of all systems that process tar files should be conducted to identify and remediate similar vulnerabilities, while adherence to the principle of least privilege should be enforced during the extraction process to minimize potential impact of successful attacks. The vulnerability also highlights the importance of secure coding practices and the need for thorough security testing of all file processing components within software systems.
The vulnerability demonstrates the critical importance of proper input validation in file system operations and represents a common pattern of insecure file handling that appears across various software ecosystems. Organizations should establish comprehensive security guidelines for all file processing operations and ensure that development teams are trained in secure coding practices to prevent similar vulnerabilities from emerging in future software releases. This particular vulnerability serves as a reminder of the persistent threat that path traversal attacks pose to system security and the necessity of maintaining current security patches and implementing defense-in-depth strategies to protect against such exploits.