CVE-2021-20035 in SMA100
Summary
by MITRE • 09/28/2021
Improper neutralization of special elements in the SMA100 management interface allows a remote authenticated attacker to inject arbitrary commands as a 'nobody' user which potentially leads to DoS.
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Analysis
by VulDB Data Team • 05/13/2025
The vulnerability identified as CVE-2021-20035 resides within the SMA100 management interface, representing a critical security flaw that enables remote authenticated attackers to execute arbitrary command injection attacks. This vulnerability stems from inadequate input validation and sanitization mechanisms within the web-based management interface of the SMA100 device, which is commonly used for solar power monitoring and management systems. The flaw specifically manifests when the system fails to properly neutralize special elements in user-supplied input, creating a pathway for malicious command injection that can be exploited by authenticated users with limited privileges.
The technical implementation of this vulnerability aligns with CWE-77 and CWE-94, which categorize improper neutralization of special elements and arbitrary code execution vulnerabilities respectively. The attack vector requires an authenticated user to leverage the system's insufficient input validation to inject malicious commands that execute with the privileges of the nobody user account. This privilege level, while limited, still provides sufficient access to potentially disrupt system operations and achieve denial of service conditions. The vulnerability operates through command injection techniques where specially crafted input bypasses security controls and gets executed within the system's command processing pipeline.
The operational impact of CVE-2021-20035 extends beyond simple command execution, as it can lead to complete system compromise and service disruption. An attacker exploiting this vulnerability can potentially cause denial of service conditions by executing commands that consume system resources, terminate critical processes, or corrupt system files. The SMA100 device's role in solar power monitoring makes this particularly concerning as it could lead to power generation disruption, data loss, or complete system failure. The vulnerability's remote nature means attackers do not require physical access to the device, making it a significant risk for distributed solar installations and industrial monitoring systems.
Mitigation strategies for this vulnerability should encompass multiple layers of defense including immediate firmware updates from the vendor to address the input validation flaws, network segmentation to limit access to the management interface, and implementation of strict access controls with minimal privilege principles. Organizations should also deploy web application firewalls to monitor and filter suspicious input patterns, conduct regular security assessments of management interfaces, and implement comprehensive monitoring for unusual command execution patterns. The ATT&CK framework categorizes this vulnerability under T1059 for command and scripting interpreters and T1499 for endpoint denial of service, indicating the need for both preventive and detection-focused security measures. Regular security patch management and network access control policies are essential to prevent exploitation of this and similar command injection vulnerabilities.