CVE-2021-27604 in NetWeaver ABAP Server
Summary
by MITRE • 04/14/2021
In order to prevent XML External Entity vulnerability in SAP NetWeaver ABAP Server and ABAP Platform (Process Integration - Enterprise Service Repository JAVA Mappings), versions - 7.10, 7.20, 7.30, 7.31, 7.40, 7.50, SAP recommends to refer this note.
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Analysis
by VulDB Data Team • 04/17/2021
The vulnerability identified as CVE-2021-27604 represents a critical XML External Entity processing flaw within SAP NetWeaver ABAP Server and ABAP Platform environments, specifically affecting the Process Integration - Enterprise Service Repository JAVA Mappings component. This vulnerability stems from insufficient input validation and sanitization of XML data processing within the SAP system architecture, creating a potential attack vector that allows malicious actors to exploit the system's handling of external entity references. The affected versions including 7.10, 7.20, 7.30, 7.31, 7.40, and 7.50 all share this common weakness in their XML parsing implementations, making them susceptible to various exploitation techniques that could compromise system integrity and data confidentiality. The vulnerability directly maps to CWE-611, which specifically addresses XML External Entity processing vulnerabilities, and aligns with ATT&CK technique T1213.002 related to data from information repositories, as attackers could potentially access sensitive system information through this vector.
The technical implementation of this vulnerability occurs when the system processes XML documents containing external entity references without proper validation mechanisms. Attackers can craft malicious XML payloads that reference external resources, potentially leading to server-side request forgery attacks, denial of service conditions, or unauthorized data access. The flaw specifically impacts the JAVA Mappings functionality within the Enterprise Service Repository, where XML processing occurs during integration and service handling operations. This processing chain lacks proper XML parser configuration to disable external entity resolution, allowing attackers to exploit the system's default behavior of resolving external references. The vulnerability is particularly concerning in enterprise environments where SAP systems often serve as central integration points for business processes, making the potential impact on system availability and data security significant.
The operational impact of CVE-2021-27604 extends beyond simple data exposure, potentially enabling attackers to perform reconnaissance activities, disrupt service availability, or gain unauthorized access to sensitive enterprise data. Organizations running affected SAP versions face risks of system compromise through indirect exploitation paths that could lead to broader network infiltration. The vulnerability's presence in multiple SAP NetWeaver versions indicates a widespread issue affecting various enterprise integration scenarios, particularly those involving process integration and service repository operations. Attackers could leverage this vulnerability to extract system information, perform unauthorized data queries, or create persistent access points within the enterprise network infrastructure. The impact is amplified in environments where SAP systems integrate with other enterprise applications, as successful exploitation could provide attackers with pathways to compromise additional systems within the organizational attack surface.
SAP has provided specific recommendations in their advisory note to address this vulnerability, emphasizing the importance of applying the recommended patches and updates to resolve the XML External Entity processing issue. Organizations should implement proper XML parser configuration to disable external entity resolution and ensure that all input validation mechanisms are properly enforced within the affected components. Security teams should also consider implementing network segmentation controls and monitoring for suspicious XML processing activities to detect potential exploitation attempts. The recommended mitigations align with industry best practices for XML security and should be implemented as part of comprehensive vulnerability management programs. Additional defensive measures include regular security assessments of SAP environments, implementation of web application firewalls with XML filtering capabilities, and establishment of robust incident response procedures specifically tailored to address SAP-related vulnerabilities. Organizations should also ensure that their security monitoring tools are configured to detect anomalous XML processing patterns that could indicate exploitation attempts.