CVE-2021-42559 in CALDERA
Summary
by MITRE • 01/12/2022
An issue was discovered in CALDERA 2.8.1. It contains multiple startup "requirements" that execute commands when starting the server. Because these commands can be changed via the REST API, an authenticated user can insert arbitrary commands that will execute when the server is restarted.
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Analysis
by VulDB Data Team • 01/15/2022
The vulnerability identified as CVE-2021-42559 resides within CALDERA version 2.8.1, a widely used adversary emulation platform designed for security testing and red team operations. This security flaw represents a critical command execution vulnerability that stems from the application's startup process and configuration handling mechanisms. The issue manifests through the platform's requirement system that executes specific commands during server initialization, creating a persistent attack surface that can be exploited by malicious actors with legitimate authentication credentials.
The technical flaw involves the improper handling of user-modifiable startup requirements within the CALDERA framework. During the server boot process, certain commands are executed automatically as part of the system initialization sequence. These commands are configured through the REST API interface, which allows authenticated users to modify these startup parameters. The vulnerability occurs because the system fails to properly validate or sanitize user input when these commands are updated, enabling an authenticated attacker to inject arbitrary shell commands that will execute with the privileges of the CALDERA server process. This design flaw directly maps to CWE-78, which describes improper neutralization of special elements used in OS commands, and CWE-94, which addresses the execution of arbitrary code due to insufficient input validation.
The operational impact of this vulnerability is severe and multifaceted, particularly for organizations that rely on CALDERA for security testing and threat emulation. An authenticated attacker can leverage this weakness to execute arbitrary commands on the system hosting the CALDERA server, potentially leading to complete system compromise. The vulnerability's exploitation requires only valid authentication credentials, making it particularly dangerous in environments where access controls may be insufficient or where credentials are compromised through other means. When the server restarts, the malicious commands are automatically executed, providing persistent access and the ability to maintain control over the compromised system. This vulnerability aligns with ATT&CK technique T1059.001, which covers command and scripting interpreter, and T1078.004, which addresses valid accounts with the specific context of compromised credentials. The attack surface extends beyond simple command execution to include potential privilege escalation, data exfiltration, and further lateral movement within the network environment.
Mitigation strategies for CVE-2021-42559 should focus on immediate patching of the CALDERA platform to version 3.0.0 or later, where this vulnerability has been addressed through proper input validation and sanitization of startup command parameters. Organizations should implement strict access controls and privilege separation, ensuring that only trusted administrators have access to the REST API endpoints that modify startup requirements. Network segmentation and monitoring of API access patterns can help detect unauthorized modifications to system configuration parameters. Additionally, implementing principle of least privilege for the CALDERA server process and regular security audits of configuration changes will help prevent exploitation. The vulnerability underscores the importance of validating all user inputs in system initialization processes and highlights the need for robust security controls in security tools themselves, as these platforms often serve as prime targets for attackers seeking persistent access to compromised environments.