CVE-2016-3635 in NetWeaver
Summary
by MITRE
SAP Netweaver 7.4 allows remote authenticated users to bypass an intended Unified Connectivity (UCON) access control list and execute arbitrary Remote Function Modules (RFM) by leveraging a connection created from earlier execution of an anonymous RFM included in a Communication Assembly, aka SAP Security Note 2139366.
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Analysis
by VulDB Data Team • 09/26/2022
The vulnerability described in CVE-2016-3635 represents a critical access control flaw within SAP Netweaver 7.4 that undermines the intended security boundaries of the Unified Connectivity (UCON) framework. This issue enables authenticated attackers to escalate their privileges and execute arbitrary Remote Function Modules through a sophisticated exploitation technique that leverages previously established communication channels. The vulnerability specifically targets the communication assembly mechanism within SAP Netweaver, where an attacker can exploit the system's handling of anonymous function calls to establish a foothold that later allows for unauthorized remote code execution. The security implications are particularly severe because this bypass affects the fundamental access control mechanisms that are designed to prevent unauthorized execution of critical system functions. The flaw demonstrates a dangerous weakness in the system's ability to maintain proper authentication state transitions between different communication contexts, creating a pathway for privilege escalation that can ultimately lead to complete system compromise.
The technical exploitation of this vulnerability relies on a specific sequence of operations involving the Communication Assembly functionality within SAP Netweaver. Attackers can initiate a connection using an anonymous Remote Function Module that is included in a Communication Assembly, which then establishes a communication context that persists beyond the initial anonymous session. This persistent connection allows subsequent authenticated users to leverage the established communication channel to bypass the intended access control list restrictions. The vulnerability is categorized under CWE-284 Access Control, which specifically addresses improper access control mechanisms in software systems. The flaw occurs because the system fails to properly validate the security context when transitioning from anonymous to authenticated sessions within the same communication assembly, creating a persistent access vector that can be exploited by malicious actors. This represents a classic case of inadequate session management and context validation, where the system's security boundaries are not properly enforced across different execution contexts.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it provides attackers with the ability to execute arbitrary Remote Function Modules that can potentially access sensitive data, modify system configurations, and perform administrative functions. The ability to execute RFMs remotely without proper authorization creates a significant threat surface that can be leveraged for data exfiltration, system disruption, and further lateral movement within the network. Organizations running SAP Netweaver 7.4 systems are particularly vulnerable because this flaw affects the core connectivity and communication infrastructure that many business-critical applications depend upon. The vulnerability also aligns with ATT&CK technique T1059 Command and Scripting Interpreter, as it enables attackers to execute arbitrary code through legitimate system interfaces. Additionally, this vulnerability supports the ATT&CK tactic T1078 Valid Accounts, as it requires only authentication to leverage existing communication channels rather than requiring additional account compromise. The persistence aspect of this vulnerability means that once exploited, attackers can maintain access through the established communication assembly connections, making detection and remediation more challenging.
Mitigation strategies for CVE-2016-3635 should focus on implementing proper access control validation and session management within the SAP Netweaver environment. Organizations should apply the official SAP Security Note 2139366 patch immediately to address the specific vulnerability in the Unified Connectivity framework. Network segmentation and monitoring should be implemented to detect unusual communication patterns that might indicate exploitation attempts, particularly around the communication assembly functionality. Access controls should be strengthened to ensure that only authorized users can establish connections through the Communication Assembly mechanism, and that proper authentication state transitions are enforced. The implementation of principle of least privilege should be enforced for all users accessing the SAP system, with particular attention to those who require access to communication assembly functionality. Regular security audits and penetration testing should be conducted to identify similar access control weaknesses in other system components. Additionally, organizations should consider implementing network-based intrusion detection systems that can monitor for suspicious communication patterns and alert security teams to potential exploitation attempts. The vulnerability highlights the importance of maintaining proper security boundaries between different execution contexts and underscores the need for robust session management mechanisms in enterprise application platforms.