CVE-2021-27632 in NetWeaver ABAP Server
Summary
by MITRE • 06/09/2021
SAP NetWeaver ABAP Server and ABAP Platform (Enqueue Server), versions - KRNL32NUC - 7.22,7.22EXT, KRNL64NUC - 7.22,7.22EXT,7.49, KRNL64UC - 8.04,7.22,7.22EXT,7.49,7.53,7.73, KERNEL - 7.22,8.04,7.49,7.53,7.73, allows an unauthenticated attacker without specific knowledge of the system to send a specially crafted packet over a network which will trigger an internal error in the system due to improper input validation in method EnqConvUniToSrvReq() causing the system to crash and rendering it unavailable. In this attack, no data in the system can be viewed or modified.
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Analysis
by VulDB Data Team • 06/11/2021
CVE-2021-27632 represents a critical denial of service vulnerability affecting SAP NetWeaver ABAP Server and ABAP Platform Enqueue Server components. This vulnerability resides in the EnqConvUniToSrvReq() method within the kernel modules of affected SAP systems, specifically impacting versions KRNL32NUC 7.22 and 7.22EXT, KRNL64NUC 7.22, 7.22EXT, and 7.49, KRNL64UC 8.04, 7.22, 7.22EXT, 7.49, 7.53, and 7.73, as well as KERNEL versions 7.22, 8.04, 7.49, 7.53, and 7.73. The flaw stems from inadequate input validation mechanisms that fail to properly sanitize incoming network packets, creating a pathway for malicious actors to exploit the system's internal error handling processes.
The technical exploitation of this vulnerability occurs when an unauthenticated attacker crafts and transmits a specially designed network packet to the affected SAP system. The malicious packet triggers an internal error within the EnqConvUniToSrvReq() method, which lacks proper validation checks for incoming data structures. This improper input validation causes the system to encounter an exception during processing, leading to a complete system crash and subsequent service disruption. The vulnerability operates at the kernel level of the SAP system architecture, making it particularly dangerous as it affects core system functionality rather than application-level components. The attack vector is entirely network-based, requiring no prior system access or credentials, which significantly increases the attack surface and exploitability.
The operational impact of CVE-2021-27632 extends beyond simple service disruption, as it can render entire SAP environments unavailable for legitimate business operations. Organizations relying on SAP NetWeaver systems for critical business processes face potential financial losses, operational downtime, and compromised business continuity. The vulnerability's nature as a denial of service attack means that while no sensitive data can be accessed or modified during exploitation, the system unavailability can severely impact enterprise operations, particularly in mission-critical applications such as ERP systems, financial processing, or supply chain management. The crash condition affects the Enqueue Server component which manages lock requests and resource coordination, making it particularly disruptive to concurrent system operations. This vulnerability aligns with CWE-20, "Improper Input Validation," and represents a classic example of how inadequate validation can lead to system instability and denial of service conditions.
Organizations should implement immediate mitigations including network-level firewall rules to restrict access to SAP Enqueue Server ports, particularly the default ports 3600-3699 used by SAP systems. SAP recommends applying the relevant security patches as soon as they become available through the SAP Security Patchday process, which addresses the root cause by implementing proper input validation in the EnqConvUniToSrvReq() method. Network segmentation strategies should be employed to limit exposure of SAP systems to untrusted networks, while monitoring solutions should be deployed to detect anomalous packet patterns that may indicate exploitation attempts. System administrators should also consider implementing intrusion detection systems that can identify and alert on suspicious network traffic targeting SAP kernel components. The vulnerability's classification under the ATT&CK framework would fall under T1499.004, "Endpoint Denial of Service," with specific techniques including T1071.004 for Application Layer Protocol: DNS and T1046 for Network Service Scanning, highlighting the multi-faceted nature of the attack surface and the importance of comprehensive defensive measures. Regular security assessments and vulnerability scanning should be conducted to identify systems running vulnerable SAP versions and ensure timely patch management processes are in place to prevent exploitation.