CVE-2021-33663 in NetWeaver AS ABAP
Summary
by MITRE • 06/09/2021
SAP NetWeaver AS ABAP, 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 - 7.22,8.04,7.49,7.53,7.73,7.77,7.81,7.82,7.83,7.84, allows an unauthorized attacker to insert cleartext commands due to improper restriction of I/O buffering into encrypted SMTP sessions over the network which can partially impact the integrity of the application.
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Analysis
by VulDB Data Team • 06/11/2021
SAP NetWeaver AS ABAP represents a critical enterprise application platform that handles sensitive business data and processes. The vulnerability described in CVE-2021-33663 specifically targets the kernel components of this platform, affecting multiple version ranges including KRNL32NUC, KRNL32UC, KRNL64NUC, KRNL64UC, and KERNEL across various releases from 7.22 through 7.84. This vulnerability resides within the cryptographic communication layer of the system, particularly impacting how the platform handles Input/Output buffering during SMTP sessions. The flaw creates a dangerous condition where unencrypted commands can be injected into encrypted communication channels, fundamentally undermining the security assurances provided by encryption protocols. Such a vulnerability directly violates the principle of secure communication and can be classified under CWE-200, which deals with information exposure, and CWE-310, which addresses cryptographic issues.
The technical mechanism behind this vulnerability involves improper restriction of I/O buffering operations within the SMTP communication stack. When the system processes email communications through encrypted channels, the buffer management fails to properly isolate cleartext commands from the encrypted session data. This allows an attacker positioned within the network to manipulate the buffer contents and inject unauthorized commands that bypass normal security controls. The attack vector leverages the network communication layer where the system expects encrypted data but receives mixed cleartext and encrypted content. The vulnerability creates a partial integrity impact because while full system compromise may not occur, the attacker can manipulate specific communication flows and potentially gain unauthorized access to sensitive data or execute unauthorized operations within the application context. This type of attack aligns with ATT&CK technique T1071.004, which covers application layer protocol usage, and T1566, focusing on credential harvesting through spearphishing.
The operational impact of this vulnerability extends beyond simple data exposure to encompass potential system integrity compromise and unauthorized access to business-critical processes. Organizations running affected SAP NetWeaver versions face significant risk of data manipulation during email communications, which could lead to financial loss, regulatory compliance violations, and reputational damage. The vulnerability affects systems that rely heavily on email notifications and automated communication processes, making it particularly dangerous for enterprise environments where email serves as a primary communication channel. Attackers could exploit this weakness to inject malicious commands that might escalate privileges or redirect communication flows, potentially leading to more severe consequences. The partial integrity impact means that while the system may continue to operate, the reliability and trustworthiness of communication channels become compromised. Organizations should consider implementing network monitoring to detect unusual communication patterns and establish robust patch management processes to address this vulnerability promptly.
Mitigation strategies for CVE-2021-33663 require immediate attention through official SAP security patches and updates. Organizations must prioritize patch deployment across all affected system versions, particularly focusing on the kernel components that handle SMTP communications. Network segmentation and monitoring should be implemented to detect potential injection attempts within email communication flows. Security teams should review and harden the configuration of SMTP settings to minimize exposure windows and implement additional authentication controls for email processing components. Regular vulnerability assessments and penetration testing should be conducted to identify similar buffer management issues in other system components. The remediation process should include thorough testing to ensure that patch deployment does not disrupt existing business processes while maintaining the security improvements. Organizations should also consider implementing network-based intrusion detection systems specifically configured to monitor for suspicious buffer manipulation patterns in encrypted communications. Additionally, administrative procedures should be updated to include regular review of email processing logs and implementation of automated alerts for unusual communication behaviors that might indicate exploitation attempts.