CVE-2021-27631 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
SAP NetWeaver ABAP Server and ABAP Platform Enqueue Server implementations contain a critical vulnerability in the EnqConvUniToSrvReq() method that allows unauthenticated remote attackers to trigger a denial of service condition. This vulnerability affects multiple kernel versions including 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 represents a classic input validation failure that occurs when processing specially crafted network packets without proper sanitization or bounds checking. This vulnerability maps directly to CWE-20, "Improper Input Validation," and aligns with ATT&CK technique T1499.004, "Endpoint Denial of Service," where adversaries exploit weaknesses in system resources to render services unavailable.
The technical mechanism of exploitation involves sending malformed network traffic that specifically targets the EnqConvUniToSrvReq() method within the enqueue server component. When this method processes the crafted input, it fails to properly validate the incoming data structure, leading to an internal error condition that causes the system to crash and become unresponsive. The vulnerability does not permit data exfiltration or modification, but the service disruption can severely impact business operations and availability. This represents a significant concern for enterprise environments where SAP systems form the backbone of critical business processes, as the denial of service can cascade through dependent applications and services.
The operational impact of this vulnerability extends beyond simple system unavailability as it can disrupt business-critical processes that depend on SAP NetWeaver infrastructure. Organizations running affected versions may experience extended downtime during attack windows, potentially affecting financial reporting, supply chain operations, and other time-sensitive business functions. The vulnerability's remote nature means attackers can exploit it from outside the network perimeter without requiring authentication credentials, making it particularly dangerous for systems exposed to the internet. Security teams must consider the potential for automated exploitation tools targeting this specific vulnerability, as it represents a low-effort, high-impact attack vector that can be weaponized at scale.
Organizations should implement immediate mitigations including applying the relevant SAP security patches released for this vulnerability, which address the input validation issues in the EnqConvUniToSrvReq() method. Network segmentation and firewall rules should be configured to limit access to SAP Enqueue Server ports from trusted networks only, while monitoring should be enabled to detect anomalous network traffic patterns that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation in server-side applications and aligns with security best practices outlined in the OWASP Top Ten and NIST Cybersecurity Framework. Regular vulnerability assessments and security testing should be conducted to identify similar input validation flaws in other SAP components and third-party applications within the enterprise environment.