CVE-2021-41243 in baserCMS
Summary
by MITRE • 11/26/2021
There is a Potential Zip Slip Vulnerability and OS Command Injection Vulnerability on the management system of baserCMS. Users with permissions to upload files may upload crafted zip files which may execute arbitrary commands on the host operating system. This is a vulnerability that needs to be addressed when the management system is used by an unspecified number of users. If you are eligible, please update to the new version as soon as possible.
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Analysis
by VulDB Data Team • 12/02/2021
The CVE-2021-41243 vulnerability represents a critical security flaw in the baserCMS management system that combines two distinct but interconnected attack vectors. This vulnerability stems from inadequate input validation and sanitization mechanisms within the file upload functionality, creating a pathway for remote code execution through maliciously crafted zip archives. The issue manifests when authorized users with file upload privileges attempt to upload specially constructed archive files that exploit weaknesses in the decompression and file extraction processes. The vulnerability is particularly concerning because it can be exploited by users who already possess legitimate access to the system, making it a privilege escalation threat that bypasses traditional authentication mechanisms.
The technical exploitation of this vulnerability involves two primary components that work in conjunction to compromise the target system. The first component is the Zip Slip vulnerability, which occurs when the application fails to properly validate directory paths within compressed archives during extraction. This allows attackers to manipulate file paths and write malicious files to arbitrary locations on the filesystem, potentially overwriting critical system files or placing backdoors in strategic directories. The second component is OS command injection, which arises from insufficient sanitization of user-supplied data within command execution contexts. When the system processes the extracted files or performs related operations, it may inadvertently execute operating system commands based on malicious input contained within the crafted zip archive. This dual nature of the vulnerability creates a particularly dangerous attack surface that can be leveraged for complete system compromise.
The operational impact of CVE-2021-41243 extends beyond simple unauthorized access, as it enables attackers to achieve persistent control over the affected system. Once successfully exploited, an attacker can execute arbitrary commands with the privileges of the web application process, potentially leading to complete system compromise, data exfiltration, or lateral movement within the network. The vulnerability's severity is amplified by its potential to affect multiple users simultaneously, as any individual with file upload permissions could serve as an attack vector. This makes the vulnerability particularly dangerous in multi-user environments where administrative privileges may be distributed across various team members. The attack requires minimal sophistication and can be automated, making it attractive to both skilled and less experienced threat actors who seek to exploit weak security controls in content management systems.
Organizations affected by this vulnerability should prioritize immediate remediation through the application of vendor-provided patches and updates. The recommended mitigation strategy involves upgrading to the latest version of baserCMS that addresses both the Zip Slip and OS command injection vulnerabilities through proper input validation, path sanitization, and command execution parameter handling. Additional defensive measures include implementing strict file type validation, disabling unnecessary file upload capabilities, and employing web application firewalls to monitor for suspicious file upload patterns. Security teams should also conduct thorough code reviews to identify similar vulnerabilities in other applications and establish robust monitoring procedures to detect exploitation attempts. This vulnerability aligns with CWE-22 (Path Traversal) and CWE-78 (OS Command Injection) categories, representing common attack patterns that frequently appear in web application security assessments and align with ATT&CK techniques for privilege escalation and execution.