CVE-2016-5995 in DB2
Summary
by MITRE
Untrusted search path vulnerability in IBM DB2 9.7 through FP11, 10.1 through FP5, 10.5 before FP8, and 11.1 GA on Linux, AIX, and HP-UX allows local users to gain privileges via a Trojan horse library that is accessed by a setuid or setgid program.
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Analysis
by VulDB Data Team • 04/18/2019
The vulnerability identified as CVE-2016-5995 represents a critical untrusted search path issue affecting IBM DB2 database installations across multiple versions and operating systems. This flaw exists within the database management system's handling of library loading processes, specifically when setuid or setgid programs execute and search for required shared libraries. The vulnerability impacts IBM DB2 versions 9.7 through Fix Pack 11, 10.1 through Fix Pack 5, 10.5 before Fix Pack 8, and 11.1 General Availability across Linux, AIX, and HP-UX platforms, creating a persistent security risk for organizations relying on these database configurations.
The technical root cause of this vulnerability stems from improper library search path handling within the DB2 installation environment. When setuid or setgid programs execute, they typically search for shared libraries in a specific order that may include directories not properly secured or validated. An attacker can exploit this by placing a malicious library file in a directory that gets searched before the legitimate system libraries, effectively causing the setuid program to load and execute the attacker-controlled code with elevated privileges. This represents a classic privilege escalation vector where the attacker leverages the database's legitimate administrative functions to gain unauthorized system access. The vulnerability aligns with CWE-426, which specifically addresses Untrusted Search Path, and demonstrates how improper library loading can lead to privilege escalation attacks. The ATT&CK framework categorizes this under privilege escalation techniques where adversaries leverage system-level programs to execute malicious code with elevated permissions.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can enable attackers to gain persistent access to database servers and potentially compromise entire database environments. Local users who can write to directories in the library search path can effectively subvert the database's security model and execute arbitrary code with the privileges of the setuid program, which often includes database administrative rights. This creates a significant risk for database administrators who may unknowingly execute compromised code while performing routine database operations. The vulnerability's persistence across multiple DB2 versions and platforms means that organizations with legacy systems or those using older fix packs remain at risk, potentially allowing attackers to maintain access even after initial exploitation attempts. The impact is particularly severe in environments where database administrators perform frequent administrative tasks through setuid programs, as each such operation presents an opportunity for exploitation.
Organizations should implement immediate mitigations including applying the relevant IBM security patches and fix packs that address this vulnerability, particularly for versions affected by CVE-2016-5995. System administrators should conduct thorough audits of library search paths and ensure that setuid programs do not search in directories where untrusted users have write permissions. The principle of least privilege should be enforced by restricting write access to library directories and implementing proper file system permissions. Additionally, organizations should consider implementing intrusion detection systems to monitor for suspicious library loading activities and regularly review system logs for signs of privilege escalation attempts. Security configurations should be updated to remove unnecessary directories from library search paths and ensure that only trusted system directories are searched for shared libraries. The remediation process must include comprehensive testing to verify that security patches do not disrupt existing database functionality while ensuring that the vulnerability is properly addressed across all affected IBM DB2 installations.