CVE-2021-27634 in NetWeaver AS for ABAP
Summary
by MITRE • 06/09/2021
SAP NetWeaver AS for ABAP (RFC Gateway), 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 - 7.22,8.04,7.49,7.53,7.73,7.77,7.81,7.82,7.83, 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 ThCpicDtCreate () causing the system to crash and rendering it unavailable. In this attack, no data in the system can be viewed or modified.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 06/11/2021
SAP NetWeaver AS for ABAP systems running various kernel versions are vulnerable to a denial of service condition that stems from inadequate input validation within the ThCpicDtCreate() method. This vulnerability affects multiple kernel variants including KRNL32NUC, KRNL64NUC, KRNL64UC, and KERNEL across several version releases. The flaw manifests when an unauthenticated attacker sends a specially crafted network packet that triggers an internal system error, causing the affected system to crash and become unavailable to legitimate users. This vulnerability falls under CWE-20, which represents improper input validation, and aligns with ATT&CK technique T1499.004 for network denial of service attacks.
The technical implementation of this vulnerability occurs within the RFC Gateway component of SAP NetWeaver, specifically within the ThCpicDtCreate() method where the system fails to properly validate incoming data structures. When malformed packets are received, the system's internal error handling mechanism becomes overwhelmed, leading to a complete system crash. The attack vector requires only network access to the target system, making it particularly dangerous as it can be exploited from remote locations without requiring any authentication credentials or prior system knowledge. The vulnerability does not permit data exfiltration or modification, but the resulting system unavailability can severely impact business operations and continuity.
The operational impact of this vulnerability extends beyond simple service disruption, as SAP NetWeaver systems often serve as critical infrastructure components within enterprise environments. Organizations relying on these systems for business-critical processes face potential financial losses, productivity impacts, and reputational damage when services become unavailable due to this attack. The vulnerability affects multiple kernel versions simultaneously, indicating a fundamental flaw in the input validation logic that has persisted across several releases. This widespread impact suggests that organizations running any of the affected kernel versions are at risk, regardless of their specific implementation or configuration.
Mitigation strategies for this vulnerability should include immediate application of SAP security notes and patches that address the specific input validation issues within the ThCpicDtCreate() method. Network segmentation and firewall rules should be implemented to restrict access to RFC gateway ports to only trusted sources, reducing the attack surface. Additionally, organizations should consider implementing intrusion detection systems that can identify and alert on suspicious network traffic patterns associated with this particular vulnerability. Monitoring for system crashes and unusual network activity should be enhanced to detect potential exploitation attempts. The vulnerability's classification under CWE-20 and its relationship to ATT&CK techniques emphasize the importance of robust input validation controls and network access restrictions as primary defense mechanisms.