CVE-2021-31893 in SIMATIC PCS 7
Summary
by MITRE • 07/13/2021
A vulnerability has been identified in SIMATIC PCS 7 V8.2 and earlier (All versions), SIMATIC PCS 7 V9.0 (All versions < V9.0 SP3), SIMATIC PDM (All versions < V9.2), SIMATIC STEP 7 V5.X (All versions < V5.6 SP2 HF3), SINAMICS STARTER (containing STEP 7 OEM version) (All versions < V5.4 HF2). The affected software contains a buffer overflow vulnerability while handling certain files that could allow a local attacker to trigger a denial-of-service condition or potentially lead to remote code execution.
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Analysis
by VulDB Data Team • 07/16/2021
This vulnerability resides within Siemens industrial automation software products including SIMATIC PCS 7, SIMATIC PDM, SIMATIC STEP 7, and SINAMICS STARTER across multiple versions. The buffer overflow occurs during file processing operations when the software fails to properly validate input data lengths before copying them into fixed-size memory buffers. This flaw represents a classic software security weakness that can be exploited by attackers with local access to the system. The vulnerability is particularly concerning in industrial control environments where these products are deployed for critical infrastructure operations, as it could potentially allow unauthorized users to disrupt operational processes or gain unauthorized access to system resources. The affected software versions span several major releases including PCS 7 V8.2 and earlier, PCS 7 V9.0 prior to SP3, PDM versions before V9.2, STEP 7 V5.X before SP2 HF3, and SINAMICS STARTER before V5.4 HF2, indicating a widespread impact across Siemens' industrial automation portfolio.
The technical implementation of this buffer overflow vulnerability stems from inadequate bounds checking within the file handling routines of these industrial software applications. When processing specific malformed or specially crafted input files, the software attempts to copy data into memory buffers without verifying that the source data size exceeds the allocated buffer capacity. This leads to memory corruption that can cause application crashes, system instability, or potentially provide a pathway for code execution. The vulnerability's classification aligns with CWE-121, which describes stack-based buffer overflow conditions, and potentially CWE-122 for heap-based buffer overflows depending on the specific implementation details. The attack surface is expanded by the fact that these industrial applications often run with elevated privileges and may be accessible through local network connections, making them attractive targets for exploitation.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions to potentially enable remote code execution within industrial control environments. In critical infrastructure settings where these Siemens products control manufacturing processes, power generation, or other essential services, such an exploit could result in significant operational disruptions, safety hazards, or even physical damage to equipment. The local attacker requirement means that an adversary would need initial access to the system, which could be achieved through various means including compromised credentials, insider threats, or exploitation of other vulnerabilities in the network infrastructure. The vulnerability's presence in industrial automation software particularly raises concerns about supply chain attacks or targeted intrusions against critical manufacturing environments where these systems operate. Organizations using these products face potential regulatory compliance issues and increased risk exposure in their operational technology environments.
Mitigation strategies should prioritize immediate software updates and patches from Siemens to address the buffer overflow conditions in affected versions. Organizations must implement comprehensive vulnerability management processes that include regular security assessments of industrial control systems and proper network segmentation to limit potential attack vectors. Access controls should be strengthened through principle of least privilege implementation, ensuring that only authorized personnel have access to industrial automation systems. Network monitoring and intrusion detection systems should be deployed to identify anomalous file processing activities that might indicate exploitation attempts. Additionally, regular security awareness training for industrial control system operators and administrators is essential to recognize potential social engineering attacks that could lead to unauthorized system access. The remediation process should also include thorough testing of patches in controlled environments before deployment to avoid operational disruptions in critical manufacturing processes. Organizations should also consider implementing application whitelisting policies and mandatory file validation procedures to reduce the risk of exploitation through malicious file uploads or processing.