CVE-2020-15186 in Helm
Summary
by MITRE
In Helm before versions 2.16.11 and 3.3.2 plugin names are not sanitized properly. As a result, a malicious plugin author could use characters in a plugin name that would result in unexpected behavior, such as duplicating the name of another plugin or spoofing the output to `helm --help`. This issue has been patched in Helm 3.3.2. A possible workaround is to not install untrusted Helm plugins. Examine the `name` field in the `plugin.yaml` file for a plugin, looking for characters outside of the [a-zA-Z0-9._-] range.
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Analysis
by VulDB Data Team • 09/18/2020
The vulnerability CVE-2020-15186 represents a critical security flaw in the Helm package manager that affects versions prior to 2.16.11 and 3.3.2. This issue stems from improper sanitization of plugin names during the Helm plugin installation and execution process, creating a potential attack vector for malicious actors. The flaw allows adversaries to craft plugin names containing special characters that can manipulate Helm's command-line interface behavior, leading to unexpected operational outcomes that could compromise system integrity.
The technical implementation of this vulnerability occurs at the plugin name validation stage within Helm's plugin management system. When Helm processes plugin installations, it fails to properly sanitize the plugin name field in the plugin.yaml configuration file. This inadequate sanitization permits the inclusion of characters outside the standard alphanumeric range and common punctuation marks, enabling attackers to craft malicious plugin names that can interfere with Helm's normal operation. The vulnerability specifically targets the help command execution where plugin names are displayed, allowing for potential spoofing of the output and confusion in command interpretation.
The operational impact of this vulnerability extends beyond simple command-line manipulation to potentially enable more sophisticated attacks within Kubernetes environments. An attacker could exploit this flaw to create plugins that duplicate legitimate plugin names, causing confusion in the Helm command interface and potentially leading to execution of unintended commands. This issue particularly affects environments where multiple users or untrusted parties have access to plugin installation capabilities, as the malicious plugin could masquerade as a legitimate component. The vulnerability creates a potential pathway for privilege escalation or information disclosure attacks that could compromise the broader Kubernetes infrastructure.
The remediation approach for this vulnerability involves upgrading to Helm versions 2.16.11 or 3.3.2 where proper sanitization of plugin names has been implemented. Organizations should immediately assess their current Helm installations and apply the necessary updates to prevent exploitation. A temporary mitigation strategy involves implementing strict validation of plugin.yaml files, specifically examining the name field for characters outside the allowed range of [a-zA-Z0-9._-]. This approach aligns with the principle of least privilege and defense in depth, ensuring that only properly formatted plugin names are accepted within the Helm ecosystem. The fix addresses the underlying CWE-20 issue related to input validation and sanitization, which is categorized under the MITRE ATT&CK framework's technique T1059 for command and scripting interpreter. Organizations should also implement comprehensive plugin management policies that restrict plugin installation to trusted sources and maintain regular audits of installed plugins to prevent unauthorized modifications.