CVE-2026-23689: Uncontrolled Resource DOS Vulnerability

CVE-2026-23689 Overview

CVE-2026-23689 is an uncontrolled resource consumption vulnerability affecting SAP systems that enables authenticated attackers to trigger denial-of-service conditions. The vulnerability exists in a remote-enabled function module that fails to properly validate loop-control parameters. An authenticated attacker with regular user privileges and network access can exploit this flaw by repeatedly invoking the vulnerable function module with excessively large loop-control parameter values.

Critical Impact

Successful exploitation enables authenticated attackers to render SAP systems unavailable through resource exhaustion, impacting business continuity and critical enterprise operations.

Affected Products

• SAP systems with remote-enabled function modules
• SAP NetWeaver Application Server (refer to SAP Note 3703092 for specific version details)

Discovery Timeline

• 2026-02-10 - CVE-2026-23689 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-23689

Vulnerability Analysis

This vulnerability falls under CWE-606 (Unchecked Input for Loop Condition), which describes scenarios where user-controlled input directly influences loop execution boundaries without proper validation. The vulnerable function module accepts a loop-control parameter that determines iteration counts for internal processing operations.

When an attacker supplies an excessively large value for this parameter, the system enters a prolonged execution state that consumes excessive CPU cycles and memory resources. The attack requires authentication with regular user privileges, meaning any legitimate user account can be leveraged to mount this attack. The vulnerability is accessible over the network, and exploitation does not require user interaction.

The scope of impact is changed (scope boundary breach), meaning the vulnerable component's exploitation affects resources beyond its security scope. While confidentiality and integrity remain unaffected, the availability impact is significant as the system can become unresponsive to legitimate requests during active exploitation.

Root Cause

The root cause stems from inadequate input validation on loop-control parameters within the remote-enabled function module. The application fails to implement proper boundary checks or resource consumption limits on user-supplied values that directly control iteration counts. This allows attackers to specify arbitrarily large values that force the system into extended processing cycles, exhausting available computational resources.

Attack Vector

The attack vector is network-based, requiring low attack complexity. An authenticated attacker with regular user privileges can exploit this vulnerability by:

1. Establishing a legitimate authenticated session to the SAP system
2. Invoking the vulnerable remote-enabled function module
3. Supplying an excessively large value for the loop-control parameter
4. Repeating the invocation to amplify resource exhaustion effects

The vulnerability can be exploited remotely without requiring physical access or additional user interaction. The prolonged loop execution triggered by malicious parameter values consumes excessive system resources, potentially rendering the application server unavailable to other users and processes.

Detection Methods for CVE-2026-23689

Indicators of Compromise

• Abnormal CPU utilization spikes correlating with function module invocations
• Extended response times or timeouts for SAP RFC (Remote Function Call) operations
• Repeated calls to remote-enabled function modules from the same user session with unusually large parameters
• System memory exhaustion events coinciding with specific function module activity

Detection Strategies

• Monitor SAP system logs for excessive invocations of remote-enabled function modules with abnormal parameter values
• Implement threshold-based alerting for CPU and memory utilization tied to specific function module execution
• Analyze RFC gateway logs for patterns of repeated calls from authenticated sessions
• Deploy application-layer monitoring to detect anomalous parameter sizes in function module calls

Monitoring Recommendations

• Enable detailed logging for RFC function module invocations including parameter values
• Configure resource utilization alerts with baselines for normal SAP application server behavior
• Implement session-based rate limiting monitoring for function module calls
• Review SAP Security Audit Log (SM21) for suspicious activity patterns

How to Mitigate CVE-2026-23689

Immediate Actions Required

• Apply the security patch detailed in SAP Note 3703092 immediately
• Review and restrict access to remote-enabled function modules to only necessary users
• Implement network segmentation to limit exposure of SAP RFC interfaces
• Monitor system resources for signs of ongoing exploitation attempts

Patch Information

SAP has released a security patch addressing this vulnerability as part of their Security Patch Day. Administrators should obtain and apply the fix documented in SAP Note 3703092. The patch implements proper input validation and resource consumption limits for the affected function module parameters. Organizations should prioritize patching based on the criticality of affected SAP systems and their exposure to authenticated users.

For complete details on affected versions and patch deployment guidance, refer to the SAP Security Patch Day portal.

Workarounds

• Restrict authorization for invoking the vulnerable remote-enabled function module using SAP authorization objects
• Implement RFC gateway security rules to limit function module accessibility
• Deploy network-level controls to restrict RFC communication paths to trusted sources only
• Consider temporarily disabling non-essential remote-enabled function modules until patching is complete