CVE-2020-4885 in DB2
Summary
by MITRE • 06/25/2021
IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) 11.5 could allow a local user to access and change the configuration of Db2 due to a race condition of a symbolic link,. IBM X-Force ID: 190909.
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Analysis
by VulDB Data Team • 06/27/2021
The vulnerability identified as CVE-2020-4885 affects IBM Db2 for Linux, UNIX and Windows including the Db2 Connect Server version 11.5, presenting a significant security risk through a race condition involving symbolic links. This issue stems from improper handling of symbolic link operations during configuration processes, creating opportunities for unauthorized access and modification of critical database system parameters. The vulnerability specifically targets local users who can exploit the timing discrepancy in symbolic link resolution to gain elevated privileges and manipulate database configurations. According to industry standards, this vulnerability maps to CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions, where the system state changes between verification and actual usage phases. The attack vector is particularly concerning as it leverages the local privilege escalation capabilities inherent in the Db2 environment, potentially allowing malicious actors with local access to compromise database integrity and availability.
The technical flaw manifests when Db2 processes symbolic links during configuration operations, where the system performs a check on the symbolic link's existence and permissions before actually accessing the target resource. This temporal gap between verification and execution creates a window where an attacker can manipulate the symbolic link target, causing the system to operate on unintended files or directories. The race condition specifically occurs in the context of configuration file handling where symbolic links are used to point to sensitive database configuration resources. This vulnerability is classified under the ATT&CK framework as part of the Privilege Escalation tactic, specifically utilizing the T1068 technique related to Exploitation for Privilege Escalation. The flaw exploits the inherent timing inconsistencies in how Db2 resolves symbolic links during critical system operations, allowing local users to potentially modify configuration files that should be protected from unauthorized access.
The operational impact of this vulnerability extends beyond simple configuration modification, as compromised Db2 configurations can lead to complete database system compromise including data exposure, unauthorized access to sensitive information, and potential disruption of database services. Local users with minimal privileges can exploit this weakness to gain elevated access to database system resources, potentially enabling them to modify database settings that control access controls, backup procedures, and other critical operational parameters. The implications are particularly severe in enterprise environments where Db2 serves as a core database management system, as successful exploitation could lead to unauthorized data access, modification of database security settings, and potential denial of service conditions. Organizations running Db2 11.5 on Linux, UNIX, and Windows platforms face significant risk if this vulnerability remains unpatched, as it provides a pathway for local attackers to escalate privileges and gain deeper access to database infrastructure.
Mitigation strategies for CVE-2020-4885 should prioritize immediate patch application from IBM, which addresses the underlying race condition in symbolic link handling within Db2 configuration processes. System administrators should implement strict file permissions and access controls on Db2 configuration directories to minimize potential exploitation opportunities, ensuring that symbolic links are properly validated and that access controls are enforced at all levels of the file system. The implementation of monitoring solutions that detect unauthorized symbolic link modifications and configuration file changes can provide early warning of potential exploitation attempts. Organizations should also consider implementing the principle of least privilege for Db2 service accounts, ensuring that local user access is restricted to only necessary functions and that symbolic link creation and modification permissions are tightly controlled. Additionally, regular security assessments and vulnerability scanning should include checks for proper symbolic link handling within database systems, as this vulnerability represents a classic example of how seemingly minor implementation flaws can create significant security risks in enterprise database environments. The mitigation approach should align with NIST cybersecurity frameworks and industry best practices for database security management, ensuring comprehensive protection against both current and potential future exploitation vectors related to symbolic link race conditions.