CVE-2016-2121 in Redis
Summary
by MITRE
A permissions flaw was found in redis, which sets weak permissions on certain files and directories that could potentially contain sensitive information. A local, unprivileged user could possibly use this flaw to access unauthorized system information.
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Analysis
by VulDB Data Team • 06/03/2023
The vulnerability identified as CVE-2016-2121 represents a critical permissions flaw within the redis database system that fundamentally compromises system security through improper file access controls. This issue manifests when redis creates certain files and directories with overly permissive access rights, specifically setting permissions that allow any local user to read sensitive data that should remain restricted. The flaw resides in the default configuration and initialization process of redis where system administrators and security professionals often overlook the importance of proper file system permissions for database components. The vulnerability directly impacts the principle of least privilege and could potentially expose confidential information including database contents, configuration files, and other sensitive operational data that resides within redis-managed directories. This type of weakness creates an attack surface that adversaries can exploit to gain unauthorized access to system resources that should be protected from casual inspection by local users.
The technical implementation of this vulnerability stems from redis's default behavior of creating temporary files and directories with world-readable permissions during its normal operation cycle. When redis starts up or performs certain operations, it generates cache files, log entries, and potentially configuration data that are stored in system directories without proper access control enforcement. The flaw allows local unprivileged users to traverse file system paths and read content that should be restricted to authorized administrators or the redis service itself. This occurs because redis does not properly implement access control lists or file permission settings that would restrict read access to only the necessary entities. The issue is particularly concerning because it requires no special privileges or network access to exploit, making it a low-effort, high-impact vulnerability that can be leveraged by any user with basic system access. This weakness aligns with CWE-732, which specifically addresses Incorrect Permission Assignment for Critical Resources, and represents a classic example of insufficient access control implementation in system components.
The operational impact of CVE-2016-2121 extends beyond simple information disclosure to potentially enable more sophisticated attacks that could compromise the overall system integrity. An attacker who successfully exploits this vulnerability gains access to potentially sensitive database contents including user credentials, session tokens, or other confidential information that could be used for further attacks. The exposure of redis configuration files might reveal database passwords, network settings, or other operational details that could aid in lateral movement within a network. Additionally, the ability to read cache files could expose patterns of data access or potentially sensitive information that was temporarily stored in memory. This vulnerability creates a persistent threat vector that remains active as long as redis is running with the default configuration, and the impact grows significantly in multi-tenant environments where multiple users share the same system resources. The vulnerability directly relates to attack techniques described in the MITRE ATT&CK framework under T1083 (File and Directory Discovery) and T1005 (Data from Local System), which detail how adversaries can enumerate system resources and extract sensitive data through unauthorized access to file systems.
Organizations affected by this vulnerability should immediately implement proper file system permission controls for redis-managed directories and files, ensuring that only authorized processes and users can access sensitive data. The recommended mitigation includes manually setting restrictive permissions on redis-created directories, implementing proper file system access controls, and regularly auditing system permissions to prevent unauthorized access. System administrators should also consider deploying redis with restricted user accounts and ensuring that the service runs with minimal necessary privileges. Regular security audits should be conducted to verify that redis installations follow secure configuration practices, including proper file ownership and access control settings. The vulnerability underscores the importance of following security best practices for database deployments and emphasizes the critical need for proper access control implementation in all system components. Organizations should also consider implementing monitoring solutions that can detect unauthorized access attempts to redis-managed files and directories, providing additional layers of protection against exploitation of this and similar vulnerabilities.