CVE-2019-20843 in Mattermost Server
Summary
by MITRE
An issue was discovered in Mattermost Server before 5.18.0, 5.17.2, 5.16.4, 5.15.4, and 5.9.7. There are weak permissions for configuration files.
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Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2019-20843 represents a critical configuration permission flaw within the Mattermost Server platform that affects multiple version lines including 5.18.0, 5.17.2, 5.16.4, 5.15.4, and 5.9.7. This issue stems from insufficient access controls governing sensitive configuration files that are essential for system operation and security posture. The weakness allows unauthorized users to potentially access or modify critical server configuration parameters that should remain protected from general user access. The vulnerability manifests as a failure to properly enforce file system permissions, creating opportunities for privilege escalation and system compromise. According to CWE classification, this corresponds to CWE-276 which addresses improper file permissions, a well-documented weakness that frequently leads to unauthorized access to sensitive system resources. The configuration files in question typically contain database credentials, encryption keys, and other sensitive parameters that could be exploited by malicious actors to gain deeper system access or extract confidential information.
The technical implementation of this vulnerability occurs when the Mattermost Server fails to properly validate file access controls during configuration file operations. This weakness enables attackers to read sensitive configuration data that should be restricted to administrative users or system processes only. The impact extends beyond simple information disclosure as compromised configuration files can reveal database connection strings, API keys, and other credentials that facilitate further exploitation. Attackers leveraging this vulnerability can potentially establish persistent access to the system by modifying configuration settings or by extracting authentication tokens and credentials stored within these files. The vulnerability aligns with ATT&CK technique T1078 which covers valid accounts and credential access, as compromised configuration files often contain the necessary authentication mechanisms for system components. When combined with other exploitation techniques, this weakness can serve as a critical initial access vector for more sophisticated attacks targeting the broader infrastructure.
The operational impact of CVE-2019-20843 can be severe for organizations relying on Mattermost Server for communication and collaboration. Compromised configuration files may lead to complete system takeover, data breaches, or unauthorized access to sensitive communications and user data. The vulnerability affects organizations across various sectors including healthcare, finance, and government agencies that use Mattermost for secure messaging platforms. System administrators may face challenges in detecting unauthorized access to configuration files, as the weakness operates at the file system level and may not generate obvious audit trail entries. The potential for lateral movement within networks increases significantly when attackers can access configuration files containing database credentials or service account information. Organizations may experience compliance violations and regulatory penalties if sensitive data is exposed due to this vulnerability, particularly in environments governed by standards such as HIPAA, PCI DSS, or SOX. The vulnerability also impacts the integrity of the communication platform, as attackers could modify configuration settings to redirect traffic or disable security features.
Mitigation strategies for CVE-2019-20843 primarily involve immediate patching of affected Mattermost Server versions to the recommended secure releases. Organizations should implement comprehensive file system permission reviews to ensure that configuration files are accessible only to authorized system processes and administrators. The principle of least privilege should be enforced by restricting access to sensitive configuration files to only those users or processes that require specific access for operational purposes. System administrators should conduct regular audits of file permissions and implement automated monitoring solutions to detect unauthorized access attempts to critical configuration files. Network segmentation and access control lists should be implemented to limit access to systems hosting Mattermost configurations. Additionally, organizations should establish robust incident response procedures that include detection and response protocols for configuration file compromise. Security monitoring solutions should be configured to alert on unusual access patterns to sensitive system files, and regular penetration testing should be conducted to verify that permission controls are properly enforced. The remediation process should also include reviewing and updating access control policies to prevent similar issues in other system components and applications.