CVE-2026-0509: SAP NetWeaver Auth Bypass Vulnerability

CVE-2026-0509 Overview

SAP NetWeaver Application Server ABAP and ABAP Platform contains an authorization bypass vulnerability that allows an authenticated, low-privileged user to perform background Remote Function Calls (RFC) without the required S_RFC authorization in certain cases. This vulnerability stems from missing authorization checks (CWE-862) in the RFC execution path, enabling attackers to execute unauthorized functions that could compromise system integrity and availability.

Critical Impact

This vulnerability allows authenticated attackers with low privileges to bypass S_RFC authorization checks, potentially enabling unauthorized system modifications and service disruptions across SAP NetWeaver environments.

Affected Products

• SAP NetWeaver Application Server ABAP
• SAP ABAP Platform
• Systems utilizing background RFC processing

Discovery Timeline

• 2026-02-10 - CVE CVE-2026-0509 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-0509

Vulnerability Analysis

This vulnerability represents a missing authorization vulnerability in SAP NetWeaver Application Server ABAP and ABAP Platform. The flaw exists in how the system handles authorization checks for background Remote Function Calls. Under certain conditions, the S_RFC authorization object—which is designed to control access to RFC-enabled function modules—is not properly validated when RFC calls are executed in background mode.

The scope change characteristic indicates that a successful exploit can affect resources beyond the vulnerable component's security authority, potentially impacting other connected SAP systems or components. While the vulnerability does not expose confidential data, it allows attackers to modify data and disrupt system availability, making it particularly dangerous for business-critical SAP environments.

Root Cause

The root cause is CWE-862: Missing Authorization. The SAP NetWeaver Application Server ABAP fails to properly enforce S_RFC authorization checks when processing background RFC requests. This oversight allows authenticated users with minimal privileges to invoke function modules they should not have access to, bypassing the intended security controls that restrict RFC execution based on user authorizations.

Attack Vector

The attack can be executed remotely over the network by any authenticated user with basic system access. The attacker does not require administrative privileges or special permissions—only valid authentication credentials. The attack does not require user interaction and can be performed programmatically, making it suitable for automated exploitation.

An attacker would authenticate to the SAP system with a low-privileged account, then initiate background RFC calls to function modules that would normally require S_RFC authorization. Because the authorization check is bypassed in certain scenarios, these calls execute successfully, allowing the attacker to perform unauthorized actions such as modifying critical business data or triggering resource-intensive operations that impact system availability.

Detection Methods for CVE-2026-0509

Indicators of Compromise

• Unexpected background RFC executions from low-privileged user accounts that lack S_RFC authorizations
• Anomalous RFC call patterns in SAP system logs, particularly background jobs initiated by users without appropriate authorization profiles
• Unauthorized modifications to business-critical data or configurations without corresponding legitimate user activity
• Unusual system performance degradation that may indicate exploitation attempts targeting availability

Detection Strategies

• Enable and monitor SAP Security Audit Log (SM21) for RFC-related events and authorization failures
• Implement SIEM correlation rules to detect background RFC executions by users lacking S_RFC authorizations
• Configure real-time alerting on RFC gateway logs for suspicious patterns from unexpected user accounts
• Perform regular authorization analysis using transaction SUIM to identify users with RFC capabilities that exceed their role requirements

Monitoring Recommendations

• Continuously monitor RFC traffic using SAP Solution Manager or third-party SAP security tools
• Establish baseline RFC execution patterns and alert on deviations, particularly for background processing
• Review ST01 authorization traces periodically to identify potential bypass attempts
• Integrate SAP logs with enterprise SIEM solutions for centralized visibility and correlation with other security events

How to Mitigate CVE-2026-0509

Immediate Actions Required

• Apply the security patch documented in SAP Note #3674774 immediately to all affected SAP NetWeaver ABAP systems
• Review and validate S_RFC authorization assignments across all user accounts to ensure least-privilege principles
• Temporarily restrict background RFC capabilities for non-essential users until patching is complete
• Enable enhanced logging for RFC activities to detect potential exploitation attempts

Patch Information

SAP has released a security update addressing this vulnerability as part of their Security Patch Day. Administrators should obtain the official patch from SAP Note #3674774 and apply it following SAP's standard patch deployment procedures. Additional security guidance is available through the SAP Security Patch Day portal.

Workarounds

• Implement strict S_RFC authorization controls by removing unnecessary RFC authorizations from user roles until the patch can be applied
• Configure RFC gateway security settings to restrict which function modules can be called remotely
• Use SAP's Unified Connectivity (UCON) framework to whitelist only required RFC-enabled function modules
• Temporarily disable background RFC processing for non-critical business processes if feasible

* Review and restrict S_RFC authorizations in user roles
* Ensure authorization object S_RFC is properly maintained:
* - RFC_TYPE: Specify allowed RFC types (e.g., 'FUNC' for function modules)
* - RFC_NAME: Restrict to specific function module names or patterns
* - ACTVT: Define permitted activities (16 = Execute)
* Consult SAP Note #3674774 for specific remediation guidance