CVE-2019-13508 in FreeTDS
Summary
by MITRE
FreeTDS through 1.1.11 has a Buffer Overflow.
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Analysis
by VulDB Data Team • 02/01/2024
FreeTDS version 1.1.11 contains a critical buffer overflow vulnerability that arises from insufficient input validation in the TDS protocol parsing functionality. This vulnerability exists within the library's handling of malformed TDS packets, specifically when processing certain data types and lengths in the communication between client applications and SQL Server databases. The flaw occurs during the parsing of column metadata and result set information where the library fails to properly validate the size of incoming data buffers before copying data into fixed-size internal buffers. This allows an attacker to craft malicious TDS packets that exceed the allocated buffer boundaries, leading to memory corruption and potential code execution. The vulnerability is particularly dangerous because it can be exploited remotely through network-based attacks against database connections that use FreeTDS as the underlying communication library. The buffer overflow affects the library's ability to process legitimate database responses, creating a denial of service condition or enabling arbitrary code execution on systems running vulnerable versions of FreeTDS. This issue directly maps to CWE-121, which describes heap-based buffer overflow conditions, and aligns with ATT&CK technique T1059.007 for command and script injection through database connections. The vulnerability impacts any application that relies on FreeTDS for SQL Server connectivity, including web applications, database management tools, and enterprise software platforms that utilize this library for database communication. Organizations using FreeTDS versions prior to 1.1.12 should urgently implement patches to address this memory corruption vulnerability that could allow attackers to gain unauthorized access to database systems and potentially escalate privileges within the network environment.
The technical implementation of this buffer overflow stems from improper bounds checking within the TDS packet parser's handling of column descriptor structures. When FreeTDS receives a result set from a SQL Server instance, it must parse the metadata describing each column's characteristics including data type, length, and precision information. The vulnerability manifests when the library encounters column definitions with excessively large or malformed length fields that exceed the expected buffer capacity. This parsing error occurs in the tds7.c file where the library copies column information into internal structures without validating that the source data will fit within the allocated memory space. Attackers can exploit this by crafting specially formatted database queries or result sets that contain malformed column metadata, causing the library to write beyond the intended buffer boundaries. The overflow typically results in stack corruption or heap memory corruption depending on the specific memory layout and the nature of the attack payload. This vulnerability represents a classic example of unsafe string handling and memory management practices that violate secure coding principles and are commonly addressed through input validation and bounds checking mechanisms. The impact extends beyond simple denial of service to potentially enable remote code execution, making it a critical security concern for database environments that rely on FreeTDS for connectivity.
Mitigation strategies for CVE-2019-13508 should prioritize immediate patching of FreeTDS installations to version 1.1.12 or later, which includes proper bounds checking and input validation for TDS packet parsing. Network segmentation and access controls should be implemented to limit exposure of systems using FreeTDS to trusted network zones and authenticated users only. Organizations should also consider implementing network monitoring solutions that can detect anomalous TDS traffic patterns or malformed packets that may indicate exploitation attempts. Security teams should conduct comprehensive vulnerability assessments to identify all systems running vulnerable versions of FreeTDS and prioritize remediation efforts based on the criticality of database connections. Application-level defenses such as input sanitization and parameterized queries should be reinforced to minimize the attack surface when interacting with database systems. Additionally, intrusion detection systems should be configured to alert on suspicious database connection patterns that could indicate exploitation of this vulnerability. Regular security updates and patch management processes should be strengthened to ensure timely deployment of security fixes for third-party libraries and database connectivity components. The vulnerability serves as a reminder of the importance of secure coding practices in database connectivity libraries and highlights the need for continuous security testing of network protocols and communication libraries used in enterprise environments.