CVE-2021-3855 in MYS
Summary
by MITRE • 03/01/2023
Improper Neutralization of Special Elements used in a Command ('Command Injection') vulnerability in Liman Central Management System Liman MYS (HTTP/Controllers, CronMail, Jobs modules) allows Command Injection.
This issue affects Liman Central Management System: from 1.7.0 before 1.8.3-462.
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Analysis
by VulDB Data Team • 05/18/2026
The CVE-2021-3855 vulnerability represents a critical command injection flaw within the Liman MYS platform, specifically impacting versions ranging from 1.7.0 through 1.8.2-462. This vulnerability resides within the HTTP/Controllers, CronMail, and Jobs modules, creating a significant security risk that can be exploited by malicious actors to execute arbitrary commands on the affected system. The flaw stems from improper neutralization of special elements used in command execution contexts, allowing attackers to inject malicious commands that bypass normal input validation mechanisms. This type of vulnerability falls under the CWE-77 category, which specifically addresses improper neutralization of special elements used in a command, making it a well-documented and dangerous class of security flaw. The attack surface is particularly concerning given that the vulnerable modules handle email processing, scheduled tasks, and job execution functions that typically operate with elevated privileges. When exploited, this vulnerability enables attackers to gain unauthorized access to the underlying system, potentially leading to complete system compromise, data exfiltration, or further lateral movement within the network. The vulnerability is particularly dangerous because it can be triggered through user-controllable inputs that are directly passed to system commands without proper sanitization or escaping.
The technical implementation of this command injection vulnerability occurs when user-provided data is directly incorporated into system commands without adequate validation or escaping mechanisms. Attackers can manipulate input fields within the HTTP/Controllers, CronMail, or Jobs modules to inject malicious command sequences that get executed by the system shell. This typically involves appending command separators such as semicolons, ampersands, or other shell metacharacters to existing commands, allowing the execution of arbitrary code with the privileges of the affected service account. The vulnerability is particularly dangerous in web applications where input validation is often insufficient, and the application may not properly escape special characters that could be interpreted by the underlying shell. The impact of this flaw extends beyond simple command execution, as it can provide attackers with persistent access to the system, enabling them to establish backdoors, install malware, or conduct further reconnaissance activities. From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter, and T1078.004 for Valid Accounts, as exploitation typically requires legitimate user credentials to trigger the vulnerable code paths.
The operational impact of CVE-2021-3855 is severe and multifaceted, potentially affecting organizations that rely on Liman MYS for email processing, automated task scheduling, and job management functions. Attackers exploiting this vulnerability can gain complete control over affected systems, leading to data breaches, system compromise, and potential disruption of business operations. The vulnerability's presence in the CronMail module particularly raises concerns about email-based attacks, where attackers could manipulate email processing workflows to execute malicious commands. Organizations running affected versions of Liman MYS are at significant risk of unauthorized access, especially if the application operates with administrative privileges or has access to sensitive data repositories. The vulnerability can also be leveraged for privilege escalation attacks, where attackers use the command injection to gain elevated system access and potentially move laterally within the network infrastructure. Additionally, the impact extends to compliance and regulatory requirements, as this vulnerability could result in violations of data protection standards and security frameworks that mandate proper input validation and command execution safeguards.
Mitigation strategies for CVE-2021-3855 should focus on immediate patching of affected systems to version 1.8.3-462 or later, which contains the necessary fixes for the command injection vulnerability. Organizations should implement comprehensive input validation and sanitization measures across all user-controllable inputs that are passed to system commands, ensuring that special characters are properly escaped or removed before command execution. The implementation of proper parameterization techniques and avoiding direct command construction from user input can significantly reduce the risk of exploitation. Security teams should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts. Regular security audits and code reviews should be conducted to identify similar vulnerabilities in other application components, particularly focusing on areas where external input is processed and executed as system commands. Additionally, organizations should establish robust monitoring and logging mechanisms to detect suspicious command execution patterns that may indicate exploitation attempts. From a defensive perspective, implementing web application firewalls and input validation rules can provide additional layers of protection, while regular security training for developers can help prevent similar vulnerabilities from being introduced in future code implementations. The remediation process should also include thorough testing to ensure that the patch does not introduce regressions in application functionality while maintaining the security improvements.