CVE-2020-25237 in SINEC NMS
Summary
by MITRE • 02/10/2021
A vulnerability has been identified in SINEC NMS (All versions < V1.0 SP1 Update 1), SINEMA Server (All versions < V14.0 SP2 Update 2). When uploading files to an affected system using a zip container, the system does not correctly check if the relative file path of the extracted files is still within the intended target directory. With this an attacker could create or overwrite arbitrary files on an affected system. This type of vulnerability is also known as 'Zip-Slip'. (ZDI-CAN-12054)
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Analysis
by VulDB Data Team • 02/26/2021
This vulnerability represents a critical path traversal flaw affecting Siemens SINEC NMS and SINEMA Server products, specifically impacting all versions prior to their respective service pack and update releases. The vulnerability stems from inadequate input validation during file extraction processes, where the system fails to properly sanitize relative file paths contained within zip archives. When an attacker uploads a malicious zip file containing specially crafted file paths, the system extracts files without proper boundary checking, allowing arbitrary file creation or overwrites on the target system. This issue directly aligns with CWE-22, which categorizes path traversal vulnerabilities as weaknesses that occur when applications fail to properly validate file paths, and specifically manifests as a Zip-Slip vulnerability as documented in the ZDI-CAN-12054 reference.
The operational impact of this vulnerability extends beyond simple file manipulation, as it provides attackers with potential persistence mechanisms and privilege escalation capabilities within industrial control systems. Attackers can leverage this vulnerability to overwrite critical system files, inject malicious code into running processes, or establish backdoor access points within the network infrastructure. The vulnerability's exploitation requires minimal privileges since the system's file extraction mechanism is typically executed with elevated permissions, making it particularly dangerous in industrial environments where system integrity is paramount. This flaw particularly affects the ATT&CK technique T1059.007 for Command and Scripting Interpreter, as it enables attackers to execute malicious code through file overwrites, and T1078.004 for Valid Accounts, since it can be used to establish persistent access through file system modifications.
Mitigation strategies should focus on immediate patch application to the affected Siemens products, with administrators ensuring all systems are updated to the latest service packs and updates. Network segmentation and access control measures should be implemented to limit exposure of these systems to untrusted users, while monitoring for suspicious file upload activities. Organizations should also implement proper input validation for all file upload mechanisms, including strict path validation and directory traversal checks. The vulnerability demonstrates the importance of following secure coding practices as outlined in OWASP Top 10 and NIST guidelines for preventing path traversal attacks. Additionally, system administrators should conduct regular security assessments and implement automated tools to detect and prevent malicious file extraction attempts, particularly in environments where industrial control systems are deployed. Regular vulnerability scanning and penetration testing should be performed to identify similar weaknesses in other industrial systems that may be susceptible to the same class of attack vectors.