CVE-2020-4053 in Helm
Summary
by MITRE
In Helm greater than or equal to 3.0.0 and less than 3.2.4, a path traversal attack is possible when installing Helm plugins from a tar archive over HTTP. It is possible for a malicious plugin author to inject a relative path into a plugin archive, and copy a file outside of the intended directory. This has been fixed in 3.2.4.
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Analysis
by VulDB Data Team • 10/24/2020
The vulnerability identified as CVE-2020-4053 represents a critical path traversal flaw affecting Helm package manager versions between 3.0.0 and 3.2.3 inclusive. This security issue specifically targets the plugin installation mechanism within Helm, creating a potential attack vector that allows malicious actors to manipulate file placement during the plugin installation process. The flaw exists in the handling of tar archives containing Helm plugins, where the system fails to properly validate or sanitize file paths contained within these archives. This vulnerability has been categorized under CWE-22 Path Traversal, which is a well-documented weakness in software systems where insufficient input validation allows attackers to access files outside of intended directories. The attack surface is particularly concerning because it leverages the trust model inherent in package management systems, where users expect that installing plugins from trusted sources will not result in arbitrary file system modifications.
The technical implementation of this vulnerability occurs when Helm processes tar archives containing plugin definitions, specifically when these archives are downloaded over HTTP. The flaw manifests through improper handling of relative path references within the tar archive structure, allowing attackers to include paths such as ../../etc/passwd or similar constructs that would traverse up the directory tree during extraction. When Helm extracts these plugin archives, it does not sufficiently validate the target paths, enabling malicious actors to place files in arbitrary locations on the system. This behavior aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: PowerShell, where attackers can manipulate installation processes to achieve unauthorized system modifications. The vulnerability essentially allows a malicious plugin author to bypass normal directory boundaries and potentially overwrite critical system files, create backdoors, or establish persistent access mechanisms.
The operational impact of CVE-2020-4053 extends beyond simple file system manipulation, as it can lead to complete system compromise when exploited in conjunction with other attack vectors. An attacker who successfully exploits this vulnerability could gain the ability to modify system configuration files, install malicious binaries, or establish persistence mechanisms within the target environment. The risk is particularly elevated in environments where Helm is used for automated deployments or where users have elevated privileges when installing plugins. This vulnerability directly impacts the security posture of Kubernetes cluster management systems, as Helm is widely used for package management in containerized environments. The exploitation of this vulnerability could result in privilege escalation, data exfiltration, or complete compromise of the underlying infrastructure. Organizations using Helm versions within the affected range face significant risk, especially when dealing with untrusted plugin sources or when automated deployment pipelines rely on plugin installations from external repositories.
Mitigation strategies for CVE-2020-4053 primarily focus on upgrading to Helm version 3.2.4 or later, which contains the necessary patches to address the path traversal vulnerability. System administrators should immediately update their Helm installations and verify that all plugin installations are performed from trusted sources. Additionally, organizations should implement strict network controls to prevent unauthorized access to plugin repositories and consider implementing network segmentation to limit the attack surface. The fix implemented in Helm 3.2.4 includes enhanced validation of file paths within tar archives, ensuring that relative paths are properly sanitized before extraction occurs. Security monitoring should be enhanced to detect unusual file system modifications, particularly around plugin installation directories, and organizations should conduct regular audits of their Helm plugin installations to identify any potentially compromised systems. Network administrators should also consider implementing content filtering and proxy configurations to prevent direct HTTP access to plugin repositories, thereby reducing the attack surface for this particular vulnerability.