CVE-2016-5423 in PostgreSQL
Summary
by MITRE
PostgreSQL before 9.1.23, 9.2.x before 9.2.18, 9.3.x before 9.3.14, 9.4.x before 9.4.9, and 9.5.x before 9.5.4 allow remote authenticated users to cause a denial of service (NULL pointer dereference and server crash), obtain sensitive memory information, or possibly execute arbitrary code via (1) a CASE expression within the test value subexpression of another CASE or (2) inlining of an SQL function that implements the equality operator used for a CASE expression involving values of different types.
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Analysis
by VulDB Data Team • 09/13/2022
The vulnerability identified as CVE-2016-5423 represents a critical security flaw in PostgreSQL database management systems affecting multiple version branches including 9.1.23, 9.2.18, 9.3.14, 9.4.9, and 9.5.4. This issue stems from improper handling of CASE expressions within the database engine's query processing logic, specifically when these expressions involve nested structures or type mismatches during function inlining operations. The flaw manifests as a NULL pointer dereference condition that can be triggered by authenticated remote attackers, creating a pathway for severe operational disruptions. According to CWE-476, this vulnerability directly maps to NULL pointer dereference conditions that occur when a program attempts to access memory through a null pointer reference, a fundamental programming error that can lead to system instability and potential code execution.
The technical implementation of this vulnerability occurs when PostgreSQL processes nested CASE expressions or when SQL functions implementing equality operators are inlined during query execution. During these operations, the database engine fails to properly validate or handle type mismatches between values being compared, particularly when different data types are involved in CASE expression evaluations. When such conditions are encountered, the system attempts to dereference a NULL pointer, causing an immediate server crash and resulting in a denial of service condition that can be exploited by remote authenticated users. The vulnerability's impact extends beyond simple service disruption as it can potentially expose sensitive memory information through the crash conditions, providing attackers with insights into the system's internal memory layout and potentially facilitating more sophisticated exploitation techniques.
The operational impact of CVE-2016-5423 presents significant risks to database availability and data integrity across affected PostgreSQL installations. Organizations utilizing these vulnerable versions face potential downtime from denial of service attacks that can be initiated by any authenticated user with access to the database system, making this a particularly dangerous vulnerability in environments where user access controls may be insufficient. The ability to potentially execute arbitrary code through this vulnerability elevates the risk beyond simple service disruption, as attackers could leverage the memory exposure to gain unauthorized access to database resources or escalate privileges within the system. This vulnerability directly aligns with ATT&CK technique T1499.004 for Denial of Service and potentially T1059 for command execution through database interfaces, making it a critical concern for cybersecurity teams managing PostgreSQL deployments.
Mitigation strategies for CVE-2016-5423 primarily focus on immediate version upgrades to patched PostgreSQL releases, with administrators strongly encouraged to upgrade to the latest available versions that contain the necessary security fixes. Organizations should also implement network-level access controls to limit authenticated database access to trusted users only, reducing the attack surface for potential exploitation. Database administrators should consider implementing query monitoring and logging to detect anomalous CASE expression usage patterns that might indicate attempted exploitation. Additionally, regular security assessments of database configurations and access controls should be performed to ensure that unauthorized users cannot leverage this vulnerability. The vulnerability's classification under CWE-476 emphasizes the importance of proper null pointer validation in database engine implementations, making code review and security testing of database components a critical requirement for maintaining system integrity.