CVE-2021-33532 in IE-WL-BL-AP-CL-EU
Summary
by MITRE • 06/26/2021
In Weidmueller Industrial WLAN devices in multiple versions an exploitable command injection vulnerability exists in the iw_webs functionality. A specially crafted diagnostic script file name can cause user input to be reflected in a subsequent iw_system call, resulting in remote control over the device. An attacker can send commands while authenticated as a low privilege user to trigger this vulnerability.
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Analysis
by VulDB Data Team • 07/02/2021
The vulnerability identified as CVE-2021-33532 represents a critical command injection flaw within Weidmueller Industrial WLAN devices that affects multiple firmware versions. This security weakness resides in the iw_webs functionality component of the device's web interface, creating a pathway for malicious actors to execute arbitrary commands on the affected systems. The vulnerability stems from insufficient input validation and sanitization mechanisms that fail to properly handle user-supplied data, particularly within diagnostic script file names.
The technical implementation of this vulnerability allows for remote code execution through a carefully crafted diagnostic script filename that gets processed by the iw_system command. When a low privilege authenticated user submits a maliciously formatted script name, the system reflects this input directly into a system call without proper sanitization. This creates a classic command injection scenario where attacker-controlled commands can be executed with the privileges of the web application process, typically corresponding to the device's system user account. The CWE-77 standard applies here as this represents a direct command injection vulnerability where user input flows into a command without proper validation or escaping.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass complete system compromise of the affected industrial wireless devices. An attacker who successfully exploits this vulnerability can gain persistent access to the network infrastructure, potentially enabling lateral movement throughout the industrial control network. The low privilege requirement for exploitation makes this particularly dangerous as it reduces the attack surface and increases the likelihood of successful compromise. This vulnerability directly maps to attack techniques documented in the ATT&CK framework under T1059.001 for command and scripting interpreter, specifically focusing on the execution of system commands through web interfaces.
Mitigation strategies for CVE-2021-33532 should prioritize immediate firmware updates from Weidmueller to address the root cause of the command injection vulnerability. Network segmentation and access control measures should be implemented to limit the blast radius of potential exploitation, particularly in industrial environments where these devices may be directly connected to operational technology networks. Additional protective measures include implementing web application firewalls to monitor and filter suspicious script name patterns, disabling unnecessary diagnostic functionality when not actively required, and establishing robust network monitoring to detect anomalous command execution patterns. Organizations should also consider implementing principle of least privilege access controls and regularly audit device configurations to prevent unauthorized modifications that could lead to exploitation of similar vulnerabilities.