CVE-2016-1249 in DBD::mysql
Summary
by MITRE
The DBD::mysql module before 4.039 for Perl, when using server-side prepared statement support, allows attackers to cause a denial of service (out-of-bounds read) via vectors involving an unaligned number of placeholders in WHERE condition and output fields in SELECT expression.
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Analysis
by VulDB Data Team • 02/17/2017
The DBD::mysql module vulnerability CVE-2016-1249 represents a critical out-of-bounds read flaw that affects Perl applications utilizing database connections through this specific database driver. This vulnerability specifically manifests when the module employs server-side prepared statement functionality, creating a scenario where malicious input can trigger memory access violations. The flaw occurs in the handling of SQL query structures that contain unaligned placeholder counts within WHERE clauses and mismatched output field specifications in SELECT expressions. The vulnerability is classified under CWE-125 as an out-of-bounds read, which falls within the broader category of memory safety issues that have historically led to system instability and potential exploitation. Attackers can leverage this weakness by crafting specially formatted SQL queries that manipulate the placeholder alignment in WHERE conditions while simultaneously controlling the output fields in SELECT statements.
The technical implementation of this vulnerability stems from improper memory management within the DBD::mysql module's prepared statement processing logic. When the module encounters a query with misaligned placeholders in WHERE conditions and corresponding output fields in SELECT expressions, it fails to properly validate the memory boundaries during the prepared statement execution phase. This misalignment creates a situation where the module attempts to read memory locations beyond the allocated buffer boundaries, resulting in an out-of-bounds read condition. The vulnerability is particularly dangerous because it can be triggered through normal database query operations without requiring special privileges or authentication. The flaw affects versions prior to 4.039, indicating that the developers had not adequately addressed memory boundary checking for specific combinations of placeholder and field count mismatches in their prepared statement implementation.
From an operational perspective, this vulnerability creates significant risk for applications that rely on DBD::mysql for database connectivity and utilize prepared statements for query execution. The denial of service impact means that an attacker can cause the application to crash or become unresponsive by submitting malicious queries that trigger the out-of-bounds read condition. This affects not only the immediate database connection but can potentially bring down entire application servers or database services that depend on the vulnerable module. The attack vector is particularly concerning because it operates at the database driver level, making it difficult to detect through standard application-level security controls. The vulnerability aligns with ATT&CK technique T1499.004 for resource exhaustion, as the out-of-bounds read can cause application instability and system resource consumption issues that may lead to complete service disruption.
The recommended mitigation strategy involves immediate upgrading of the DBD::mysql module to version 4.039 or later, where the memory boundary checking has been properly implemented to handle unaligned placeholder scenarios. Organizations should also implement comprehensive input validation for all SQL queries, particularly those involving prepared statements, to prevent malformed queries from reaching the vulnerable module. Security monitoring should include detection of unusual query patterns that might indicate attempts to exploit this vulnerability, such as queries with mismatched placeholder and field counts. Additionally, application developers should consider implementing query parameter sanitization and boundary checking within their applications to add an additional layer of protection against this type of memory safety issue. The vulnerability demonstrates the importance of thorough testing for memory safety conditions in database drivers, particularly when handling prepared statement functionality that processes user-supplied data.