CVE-2020-8570 in Java Client
Summary
by MITRE • 01/22/2021
Kubernetes Java client libraries in version 10.0.0 and versions prior to 9.0.1 allow writes to paths outside of the current directory when copying multiple files from a remote pod which sends a maliciously crafted archive. This can potentially overwrite any files on the system of the process executing the client code.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 02/13/2021
The vulnerability identified as CVE-2020-8570 affects the Kubernetes Java client libraries and represents a critical directory traversal flaw that enables attackers to manipulate file operations beyond intended boundaries. This vulnerability specifically impacts versions 10.0.0 and earlier releases, with the issue being resolved in version 9.0.1 and subsequent releases. The flaw manifests when the client library processes multiple file copies from remote pods, particularly when handling maliciously crafted archive files that contain path traversal sequences. This vulnerability falls under the CWE-22 category for Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal or directory traversal attacks.
The technical implementation of this vulnerability occurs during the file extraction process where the Kubernetes Java client fails to properly validate or sanitize file paths contained within archive files. When a malicious archive is processed, the client library does not adequately restrict the destination paths, allowing attackers to craft archive contents that include directory traversal sequences such as "../" or similar path manipulation patterns. This allows the extraction process to write files to arbitrary locations on the filesystem where the client process has write permissions, potentially enabling attackers to overwrite critical system files, configuration files, or even inject malicious code into the execution environment.
The operational impact of this vulnerability extends beyond simple file overwrites and represents a significant escalation risk for Kubernetes environments. An attacker who can influence the content of archives being processed by a Kubernetes Java client can potentially compromise the entire system where the client is executing. This risk is particularly severe in containerized environments where the client might run with elevated privileges or in scenarios where the client process has access to sensitive system resources. The vulnerability can be exploited through various attack vectors including compromised pods, malicious image registries, or by intercepting network traffic between the client and remote pods. According to ATT&CK framework, this vulnerability maps to T1059.007 for Command and Scripting Interpreter: Python and potentially T1566.001 for Phishing: Spearphishing Attachment, depending on how the malicious archive is delivered.
Mitigation strategies for CVE-2020-8570 require immediate action to update the affected Kubernetes Java client libraries to versions 9.0.1 or later where the vulnerability has been patched. Organizations should implement comprehensive inventory tracking of all systems utilizing the Kubernetes Java client to ensure complete remediation across their infrastructure. Additional defensive measures include implementing strict file validation controls on archive processing, deploying network segmentation to limit access to Kubernetes APIs, and establishing monitoring for unusual file system activities that might indicate exploitation attempts. The patch addresses the core issue by implementing proper path validation and normalization within the archive extraction routines, ensuring that all file paths are properly constrained to the intended directory structure. Security teams should also consider implementing runtime protections such as file system access controls and privilege separation to limit the potential impact even if exploitation occurs. Regular security assessments and vulnerability scanning should be conducted to identify any other potentially affected components within the Kubernetes ecosystem that might be vulnerable to similar path traversal attacks.