CVE-2021-33485 in Control Runtime System
Summary
by MITRE • 08/03/2021
CODESYS Control Runtime system before 3.5.17.10 has a Heap-based Buffer Overflow.
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Analysis
by VulDB Data Team • 05/30/2026
The CVE-2021-33485 vulnerability represents a critical heap-based buffer overflow flaw within the CODESYS Control Runtime system affecting versions prior to 3.5.17.10. This vulnerability resides in the industrial automation software ecosystem, specifically within the runtime environment that executes control applications on embedded systems and industrial controllers. The flaw manifests when the system processes certain input data structures that exceed allocated buffer boundaries, creating opportunities for malicious actors to exploit memory corruption vulnerabilities.
The technical implementation of this buffer overflow occurs due to insufficient bounds checking during memory allocation and data processing operations within the CODESYS Control Runtime environment. When the system receives malformed input or processes data streams that exceed predetermined buffer limits, the heap memory management routines fail to validate input lengths properly, leading to memory overwrite conditions. This vulnerability falls under the CWE-121 heap-based buffer overflow category, which is classified as a fundamental memory safety issue that can lead to arbitrary code execution or system crashes. The flaw is particularly concerning in industrial control environments where system stability and security are paramount.
The operational impact of this vulnerability extends beyond simple system instability to encompass potential safety risks in industrial environments. Attackers exploiting this vulnerability could gain unauthorized access to control systems, potentially disrupting critical infrastructure operations or manipulating industrial processes. The attack surface is particularly wide given that CODESYS Control Runtime is deployed across various industrial sectors including manufacturing, energy, and process control systems. The vulnerability could enable attackers to execute arbitrary code with elevated privileges, potentially leading to complete system compromise. This aligns with ATT&CK technique T1059.007 for command and scripting interpreter, where attackers might leverage the overflow to establish persistent access or escalate privileges within the control environment.
Mitigation strategies for CVE-2021-33485 primarily focus on immediate software updates to versions 3.5.17.10 and later, which contain proper bounds checking mechanisms and memory validation routines. Organizations should implement network segmentation and access controls to limit exposure of affected systems to external threats. Additional defensive measures include deploying intrusion detection systems that monitor for anomalous memory access patterns and implementing runtime application self-protection mechanisms. Regular security assessments of industrial control systems should include vulnerability scanning for similar memory corruption flaws, particularly in legacy systems that may not receive regular updates. The vulnerability also underscores the importance of secure coding practices in industrial software development, emphasizing the need for comprehensive input validation and memory management procedures that align with industry standards such as IEC 62443 for industrial automation and control systems security.