CVE-2019-20856 in Mattermost Desktop App
Summary
by MITRE
An issue was discovered in Mattermost Desktop App before 4.3.0 on macOS. It allows dylib injection.
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Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2019-20856 represents a significant security flaw in the Mattermost Desktop Application for macOS systems prior to version 4.3.0. This issue enables malicious actors to perform dynamic library injection attacks, which can compromise the integrity and confidentiality of user data processed through the application. The vulnerability specifically affects the desktop application's handling of dynamic library loading mechanisms on macOS platforms, creating an attack surface that adversaries can exploit to execute arbitrary code within the application's context.
The technical flaw stems from improper validation of dynamic library paths and loading mechanisms within the Mattermost desktop application. When the application loads shared libraries, it fails to properly sanitize or verify the source and integrity of these libraries, allowing attackers to inject malicious dynamic libraries that can be loaded alongside legitimate ones. This weakness aligns with CWE-427 Uncontrolled Search Path Element, which describes how applications that do not properly control the search paths for dynamic libraries can be exploited through injection attacks. The vulnerability essentially allows an attacker to manipulate the application's dynamic linking behavior, potentially leading to privilege escalation or data exfiltration.
The operational impact of this vulnerability extends beyond simple code execution, as it can enable attackers to gain persistent access to user systems through the Mattermost application. Since Mattermost is commonly used for enterprise communication and collaboration, successful exploitation could provide attackers with access to sensitive business communications, credentials, and other confidential information. The attack vector typically involves placing a malicious dylib file in a location that gets loaded before the legitimate library, leveraging the application's trust in the standard library loading process. This type of attack aligns with ATT&CK technique T1574.006 Dynamic Linker Hijacking, which specifically targets the dynamic linking process to achieve persistence and privilege escalation.
Mitigation strategies for CVE-2019-20856 primarily involve updating to Mattermost Desktop App version 4.3.0 or later, which includes proper validation of dynamic library loading. Organizations should also implement application whitelisting policies to restrict which libraries can be loaded, employ code signing verification mechanisms, and monitor for unusual library loading patterns. Additionally, security teams should consider implementing macOS security controls such as System Integrity Protection (SIP) enforcement and regular security audits of desktop applications to prevent similar vulnerabilities from being exploited in other software products. The vulnerability demonstrates the critical importance of proper library loading security practices in desktop applications, particularly those handling sensitive enterprise data.