CVE-2019-3693 in Linux Enterprise Server
Summary
by MITRE
A symlink following vulnerability in the packaging of mailman in SUSE Linux Enterprise Server 11, SUSE Linux Enterprise Server 12; openSUSE Leap 15.1 allowed local attackers to escalate their privileges from user wwwrun to root. Additionally arbitrary files could be changed to group mailman. This issue affects: SUSE Linux Enterprise Server 11 mailman versions prior to 2.1.15-9.6.15.1. SUSE Linux Enterprise Server 12 mailman versions prior to 2.1.17-3.11.1. openSUSE Leap 15.1 mailman version 2.1.29-lp151.2.14 and prior versions.
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Analysis
by VulDB Data Team • 03/26/2024
The vulnerability described in CVE-2019-3693 represents a critical privilege escalation flaw within the mailman package distribution on various SUSE and openSUSE Linux systems. This issue stems from improper handling of symbolic links during package installation or execution processes, creating a path traversal condition that allows unprivileged local users to gain elevated system privileges. The vulnerability specifically targets the wwwrun user account which typically runs web server processes and enables attackers to escalate their access level to root privileges, fundamentally compromising system security boundaries. The flaw manifests when the mailman package processes symbolic links without adequate validation, potentially allowing attackers to manipulate file permissions and ownership during package operations.
The technical implementation of this vulnerability involves a classic symlink following attack vector where maliciously crafted symbolic links can be exploited during package installation or update procedures. When mailman processes these links, it follows them without proper sanitization checks, enabling attackers to redirect file operations to arbitrary locations on the filesystem. This behavior aligns with CWE-367, which describes Time-of-Check to Time-of-Use (TOCTOU) vulnerabilities, where the system's state changes between verification and execution phases. The vulnerability particularly affects the mailman package's handling of file permissions and group assignments, allowing attackers to modify files owned by the mailman group and potentially gain root access through privilege escalation mechanisms. The specific conditions require the attacker to have local access to the system and the ability to manipulate package installation processes or create symbolic links in locations that mailman processes.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete control over affected systems. Once escalated to root privileges, attackers can modify system files, install backdoors, exfiltrate sensitive data, and establish persistent access to the compromised infrastructure. The vulnerability affects multiple enterprise Linux distributions including SUSE Linux Enterprise Server 11 and 12, as well as openSUSE Leap 15.1, making it a widespread concern for organizations using these platforms. The ability to change file ownership to the mailman group further compounds the risk, as it can potentially allow attackers to modify critical system components or configuration files that are normally protected. This vulnerability particularly impacts web applications and mail services running on these systems, as the wwwrun user typically handles mail processing tasks and is directly involved in the vulnerable code paths.
Organizations should immediately implement mitigation strategies including updating to patched versions of the mailman package as specified in the affected versions. The recommended remediation involves upgrading to mailman versions 2.1.15-9.6.15.1 for SUSE Linux Enterprise Server 11, 2.1.17-3.11.1 for SUSE Linux Enterprise Server 12, and the appropriate versions for openSUSE Leap 15.1. System administrators should also implement proper file system permissions and ensure that symbolic link handling is properly validated in all package management operations. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the T1068 - Exploitation for Privilege Escalation tactic, where adversaries leverage software vulnerabilities to gain higher-level permissions. Additionally, this vulnerability demonstrates characteristics of T1548.001 - Abuse Elevation Control Mechanism, where attackers exploit system weaknesses to bypass security controls. Organizations should conduct comprehensive security audits to identify systems running vulnerable mailman versions and implement monitoring for suspicious file system changes or privilege escalation attempts. Regular patch management processes should be strengthened to ensure timely deployment of security updates and prevent similar vulnerabilities from being exploited in the future.