CVE-2019-14463 in libmodbus
Summary
by MITRE
An issue was discovered in libmodbus before 3.0.7 and 3.1.x before 3.1.5. There is an out-of-bounds read for the MODBUS_FC_WRITE_MULTIPLE_REGISTERS case, aka VD-1301.
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Analysis
by VulDB Data Team • 11/14/2023
The vulnerability identified as CVE-2019-14463 represents a critical out-of-bounds read flaw affecting libmodbus versions prior to 3.0.7 and 3.1.x versions before 3.1.5. This issue specifically manifests within the MODBUS_FC_WRITE_MULTIPLE_REGISTERS function call case, which is a fundamental operation in modbus protocol implementations used extensively in industrial control systems and SCADA networks. The vulnerability falls under the category of memory safety issues and is classified as CWE-125: Out-of-bounds Read according to the Common Weakness Enumeration standards. The flaw occurs when processing write multiple registers requests, where the software fails to properly validate input parameters before attempting to access memory regions beyond the allocated buffer boundaries.
The technical implementation of this vulnerability stems from insufficient bounds checking within the modbus protocol handler when processing the write multiple registers function code. When a client sends a MODBUS_FC_WRITE_MULTIPLE_REGISTERS request containing a malformed or excessively large quantity of registers to write, the libmodbus library does not adequately validate the length parameter against the actual buffer size. This allows an attacker to craft malicious requests that cause the software to read memory locations that are not properly allocated for the operation. The vulnerability is particularly dangerous because it can be exploited through network-based attacks without requiring authentication, making it accessible to remote threat actors who can manipulate the protocol communication layer.
From an operational impact perspective, this vulnerability poses significant risks to industrial control systems that rely on libmodbus for communication between devices and supervisory systems. The out-of-bounds read can potentially lead to information disclosure, system instability, or even remote code execution depending on the specific implementation and memory layout of the affected systems. The attack surface is particularly wide given that modbus protocol is widely deployed in critical infrastructure sectors including power generation, water treatment, manufacturing, and transportation systems. The vulnerability can be exploited by attackers to gather sensitive information from memory, potentially exposing system configurations, credentials, or other confidential data that may be stored in adjacent memory regions.
The exploitation of this vulnerability aligns with several techniques documented in the MITRE ATT&CK framework, particularly under the T1059.007 sub-technique for Command and Scripting Interpreter: Python and T1566.001 for Phishing: Spearphishing Attachment. Attackers can leverage this flaw to perform reconnaissance activities by reading memory contents that may reveal system information, or they can use it as a stepping stone for more sophisticated attacks. The vulnerability also maps to ATT&CK technique T1210: Exploitation of Remote Services, as it enables remote code execution capabilities through protocol manipulation. Organizations using affected libmodbus versions should implement immediate mitigations including patching to the latest stable releases, network segmentation, and monitoring for suspicious modbus traffic patterns. Additionally, the vulnerability highlights the importance of proper input validation and bounds checking in industrial communication protocols, emphasizing the need for security-by-design principles in critical infrastructure software development. The issue demonstrates how seemingly minor implementation flaws in widely-used libraries can create significant security risks in operational technology environments where system reliability and security are paramount considerations.