CVE-2016-0767 in PostgreSQL PL-Java
Summary
by MITRE
PostgreSQL PL/Java before 1.5.0 allows remote authenticated users with USAGE permission on the public schema to alter the public schema classpath.
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Analysis
by VulDB Data Team • 10/14/2019
The vulnerability identified as CVE-2016-0767 affects PostgreSQL PL/Java extensions prior to version 1.5.0, representing a significant privilege escalation issue within database security frameworks. This flaw resides in the PL/Java extension mechanism that allows java-based stored procedures to be executed within PostgreSQL environments, creating a complex attack surface where database permissions can be leveraged to manipulate core database schema configurations. The vulnerability specifically targets the public schema classpath manipulation capabilities, which serve as critical pathways for extending database functionality through java libraries and custom code execution.
The technical flaw manifests through improper access control mechanisms within the PL/Java extension implementation. When authenticated users possess USAGE permission on the public schema, they can exploit a design oversight to modify the classpath configuration that governs how PostgreSQL resolves and loads java classes. This occurs because the extension does not properly validate whether the requesting user has appropriate authorization levels to alter schema-level classpath settings. The vulnerability stems from inadequate input validation and privilege checking within the PL/Java runtime environment, allowing attackers to inject malicious classpath entries that could potentially lead to arbitrary code execution or further privilege escalation within the database system.
Operationally, this vulnerability presents a serious risk to database security as it enables authenticated attackers to elevate their privileges within the database environment. The impact extends beyond simple schema modification since altering the classpath can potentially allow attackers to load malicious java libraries that execute arbitrary code with the privileges of the database user. This creates a potential attack vector for lateral movement within database networks, especially in environments where database users have broader permissions than strictly necessary. The vulnerability is particularly concerning in multi-tenant database environments where different users share the same database instance but should maintain isolated privilege levels.
Organizations should immediately upgrade to PL/Java version 1.5.0 or later to remediate this vulnerability, as no effective workarounds exist that maintain full functionality while addressing the core privilege escalation issue. The recommended mitigation strategy involves implementing principle of least privilege for database users, ensuring that only authorized personnel possess USAGE permissions on the public schema. Database administrators should also conduct comprehensive audits of existing user permissions and classpath configurations to identify any potential exploitation attempts. Security monitoring should be enhanced to detect unusual schema modification patterns and unauthorized classpath changes. This vulnerability aligns with CWE-284 (Improper Access Control) and represents a classic example of how extension mechanisms can introduce security gaps when proper privilege boundaries are not maintained. The attack pattern follows ATT&CK technique T1078 (Valid Accounts) combined with T1059 (Command and Scripting Interpreter) through the exploitation of database extension capabilities.