CVE-2021-27628 in NetWeaver ABAP Server
Summary
by MITRE • 06/09/2021
SAP NetWeaver ABAP Server and ABAP Platform (Dispatcher), versions - KRNL32NUC - 7.22,7.22EXT, KRNL32UC - 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 DpRTmPrepareReq() 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-2021-27628 represents a critical denial of service vulnerability affecting SAP NetWeaver ABAP Server and ABAP Platform components across multiple kernel versions. This vulnerability resides in the DpRTmPrepareReq() method within the dispatcher functionality, where insufficient input validation creates a pathway for remote exploitation. The flaw manifests when an unauthenticated attacker crafts and transmits a specially formatted network packet that triggers an internal system error, resulting in complete service disruption. This vulnerability aligns with CWE-20, which catalogs "Improper Input Validation" as a fundamental weakness in software design that can lead to various security issues including denial of service conditions.
The technical implementation of this vulnerability demonstrates a classic buffer overflow or input parsing issue within the ABAP dispatcher's request processing logic. When the system receives malformed input through the DpRTmPrepareReq() method, it fails to properly validate the incoming data structure before processing, leading to an internal error condition that causes the system to terminate unexpectedly. The affected kernel versions span across multiple release lines including 7.22, 7.49, 8.04, and several others, indicating this is a long-standing issue that has persisted across multiple SAP NetWeaver releases. The attack vector requires only network connectivity without any authentication requirements, making it particularly dangerous as it can be exploited by any remote attacker.
From an operational impact perspective, this vulnerability creates a severe availability risk for SAP systems that have not been patched. The system crash resulting from exploitation renders the entire ABAP platform unavailable until manual intervention or system restart occurs, potentially causing significant business disruption. Organizations running SAP NetWeaver systems in production environments face the risk of extended downtime, especially if they operate critical business applications that depend on these platforms. The vulnerability does not permit data exfiltration or modification, but the availability impact can be substantial for enterprises relying on continuous SAP system operations. This aligns with ATT&CK technique T1499.004 which covers "Endpoint Denial of Service" and represents a significant concern for enterprise security teams managing SAP infrastructure.
The mitigation strategy for CVE-2021-27628 requires immediate implementation of SAP security patches released for affected kernel versions. Organizations should prioritize patching their SAP NetWeaver systems as soon as possible, particularly those running the vulnerable kernel versions mentioned in the advisory. Network segmentation and firewall rules can provide temporary protection by restricting access to SAP dispatcher ports, though this approach does not eliminate the vulnerability entirely. Additionally, monitoring for unusual network traffic patterns or system crashes can help detect exploitation attempts. SAP recommends applying the relevant kernel updates and security notes as outlined in their official security bulletins. System administrators should also consider implementing intrusion detection systems to monitor for potential exploitation attempts targeting this specific vulnerability, as the attack can be automated and may occur without prior warning signs.