CVE-2020-6366 in NetWeaver
Summary
by MITRE • 10/20/2020
SAP NetWeaver (Compare Systems) versions - 7.20, 7.30, 7.40, 7.50, does not sufficiently validate uploaded XML documents. An attacker with administrative privileges can retrieve arbitrary files including files on OS level from the server and/or can execute a denial-of-service.
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Analysis
by VulDB Data Team • 11/21/2020
SAP NetWeaver Compare Systems vulnerability CVE-2020-6366 represents a critical security flaw in multiple versions of the SAP NetWeaver platform that enables unauthorized file access and denial-of-service attacks. This vulnerability specifically affects versions 7.20, 7.30, 7.40, and 7.50 of the Compare Systems component within SAP NetWeaver. The flaw stems from inadequate validation of XML document uploads, creating a pathway for malicious actors to exploit the system's file handling mechanisms. The vulnerability is particularly dangerous because it allows attackers with administrative privileges to access arbitrary files on the server, including sensitive operating system level files that should remain protected. This represents a severe violation of the principle of least privilege and demonstrates a critical failure in input validation controls that should prevent such unauthorized access patterns.
The technical implementation of this vulnerability involves XML external entity processing where the system fails to properly sanitize uploaded XML documents before processing them. When an attacker uploads a malicious XML file, the system does not adequately validate the document structure or content, allowing XML entities to reference local files on the server. This weakness directly maps to CWE-611, which describes improper restriction of XML external entity reference, and aligns with ATT&CK technique T1059.007 for execution through XML files. The vulnerability creates a direct path for attackers to traverse the file system and access sensitive data, potentially including configuration files, database credentials, and other system artifacts that could compromise the entire infrastructure. The lack of proper XML schema validation and entity resolution restrictions means that attackers can craft XML documents that reference arbitrary file paths and retrieve their contents through the application's processing pipeline.
The operational impact of this vulnerability extends beyond simple data theft to include significant system compromise and service disruption. Attackers can leverage this flaw to execute denial-of-service attacks by uploading malicious XML documents that cause the application to consume excessive resources or crash entirely. The ability to read operating system level files provides attackers with comprehensive information about the system configuration, potentially exposing database connection strings, encryption keys, and other critical system components. This vulnerability essentially provides a backdoor into the system that allows for lateral movement and further exploitation. The impact is amplified by the fact that the vulnerability requires only administrative privileges to exploit, meaning that attackers who have already gained administrative access can use this flaw to escalate their compromise and access even more sensitive information. Organizations running these affected SAP NetWeaver versions face significant risk of data breaches, system downtime, and potential regulatory compliance violations.
Mitigation strategies for CVE-2020-6366 should focus on immediate patching and configuration hardening to prevent exploitation. SAP has released patches addressing this vulnerability, and organizations should prioritize applying these updates to all affected systems. Additionally, implementing proper XML validation controls and disabling unnecessary XML external entity processing can significantly reduce the risk of exploitation. Network segmentation and access controls should be implemented to limit administrative privileges and reduce the attack surface. Organizations should also establish monitoring procedures to detect unusual file upload activities and implement automated scanning for malicious XML content. The vulnerability highlights the importance of proper input validation and the need for organizations to maintain current security patches across all SAP components. Regular security assessments and vulnerability scanning should be conducted to identify similar flaws in other system components. The incident underscores the necessity of following security best practices such as the principle of least privilege and defense in depth strategies to protect against sophisticated attacks that exploit multiple system weaknesses.