CVE-2016-0768 in PostgreSQL PL-Java
Summary
by MITRE
PostgreSQL PL/Java after 9.0 does not honor access controls on large objects.
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Analysis
by VulDB Data Team • 10/14/2019
PostgreSQL PL/Java represents a critical security vulnerability classified as CVE-2016-0768 that emerged within the PostgreSQL database management system's Java procedural language extension. This vulnerability specifically affects PostgreSQL versions post-9.0 where the PL/Java extension fails to properly enforce access controls when handling large objects within the database environment. The flaw resides in the implementation of the large object functionality where the extension does not adequately validate user permissions before allowing operations on large objects, creating a potential pathway for unauthorized data access and manipulation.
The technical nature of this vulnerability stems from a failure in privilege enforcement mechanisms within the PL/Java extension module. When database users execute Java functions that interact with large objects, the system should verify that the executing user possesses appropriate permissions to perform the requested operations. However, the vulnerability allows for bypassing these access controls, enabling malicious users to read, modify, or delete large objects without proper authorization. This represents a direct violation of the principle of least privilege and undermines the fundamental security model of the database system.
The operational impact of CVE-2016-0768 extends beyond simple unauthorized access to encompass potential data breaches and system compromise. Attackers could exploit this vulnerability to extract sensitive information stored in large objects, which often contain critical business data, personal information, or proprietary content. The vulnerability particularly affects environments where PostgreSQL is used for enterprise applications that rely heavily on large object storage for documents, images, or binary data. Additionally, the issue can facilitate privilege escalation attacks where users with limited database access gain broader capabilities through manipulation of large objects.
Security practitioners should recognize this vulnerability as a clear example of improper access control implementation, which aligns with CWE-284, Access Control. The attack surface for this vulnerability is particularly concerning in multi-tenant database environments where different users share the same PostgreSQL instance but should maintain strict data isolation. Organizations using PostgreSQL with PL/Java extensions should immediately implement mitigations including applying the latest security patches from PostgreSQL and the PL/Java project maintainers. Database administrators should also review and tighten access controls for large object operations, implement additional monitoring for suspicious large object access patterns, and consider restricting PL/Java function execution to trusted database users only. The vulnerability demonstrates the importance of comprehensive security testing for database extensions and the critical need for proper privilege validation in all database interaction points, particularly those involving complex data types like large objects that are commonly used in enterprise database applications.