CVE-2026-27689: Uncontrolled Resource Consumption DoS Flaw

CVE-2026-27689 Overview

CVE-2026-27689 is an uncontrolled resource consumption vulnerability affecting SAP systems that allows authenticated attackers with regular user privileges to cause a denial-of-service condition. By repeatedly invoking a remote-enabled function module with an excessively large loop-control parameter, attackers can trigger prolonged loop execution that consumes excessive system resources, potentially rendering the system unavailable.

Critical Impact

Authenticated attackers can exploit this vulnerability to cause system-wide denial of service, disrupting business operations and affecting system availability for all users.

Affected Products

• SAP systems with remote-enabled function modules (refer to SAP Note #3719502 for specific affected versions)

Discovery Timeline

• 2026-03-10 - CVE-2026-27689 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2026-27689

Vulnerability Analysis

This vulnerability is classified as CWE-606: Unchecked Input for Loop Condition. The flaw exists in a remote-enabled function module that fails to properly validate the loop-control parameter before processing. When an attacker supplies an excessively large value for this parameter, the system enters a prolonged loop execution state that consumes excessive CPU and memory resources.

The attack requires network access and authentication with regular user privileges, meaning any authenticated user on the network can potentially exploit this vulnerability. While the attack does not compromise data confidentiality or integrity, the scope is changed, meaning the vulnerable component's impact extends beyond its own security scope and affects other components in the system.

Root Cause

The root cause of this vulnerability is the absence of proper input validation on the loop-control parameter within the remote-enabled function module. The application accepts user-supplied values without verifying they fall within acceptable bounds, allowing attackers to specify arbitrarily large values that cause resource exhaustion.

This type of vulnerability occurs when:

• Loop iteration counts are derived from untrusted input
• No upper bounds are enforced on iteration counts
• Resource consumption is not monitored or limited during execution

Attack Vector

The attack is network-based and requires the attacker to have valid authentication credentials with at least regular user privileges. The attacker exploits the vulnerability by:

1. Establishing an authenticated session to the target SAP system
2. Identifying the vulnerable remote-enabled function module
3. Invoking the function with an excessively large loop-control parameter value
4. Repeating the invocation to amplify resource consumption
5. System resources become exhausted, causing denial of service

The attack complexity is low, requiring no user interaction, making it easily repeatable and automatable once valid credentials are obtained.

Detection Methods for CVE-2026-27689

Indicators of Compromise

• Abnormal CPU utilization spikes on SAP application servers
• Unusually high memory consumption by SAP work processes
• Repeated invocations of the same remote function module from a single user account
• System performance degradation or unresponsiveness during normal business hours
• Increased response times for RFC (Remote Function Call) operations

Detection Strategies

• Monitor SAP system logs for repeated calls to remote-enabled function modules with unusual parameter values
• Implement anomaly detection for function module invocation patterns
• Configure alerting for resource consumption thresholds being exceeded
• Review SAP Security Audit Log (SM21) for suspicious user activity patterns
• Enable SAP Gateway logging to track RFC calls and identify abuse patterns

Monitoring Recommendations

• Configure real-time monitoring of CPU and memory utilization on SAP application servers
• Establish baseline metrics for normal function module invocation rates
• Implement user behavior analytics to detect anomalous RFC activity
• Set up automated alerts when resource consumption exceeds defined thresholds
• Monitor work process availability and queue depths in SAP transaction SM50/SM66

How to Mitigate CVE-2026-27689

Immediate Actions Required

• Apply the security patch referenced in SAP Note #3719502
• Review and restrict authorization for remote function module access
• Implement network segmentation to limit access to SAP RFC interfaces
• Enable enhanced logging for remote function module invocations
• Consider implementing rate limiting for RFC calls where possible

Patch Information

SAP has released a security patch to address this vulnerability as part of their Security Patch Day program. Organizations should apply the patch referenced in SAP Note #3719502 as soon as possible. The patch implements proper input validation for the loop-control parameter to prevent exploitation.

For detailed patching instructions and affected version information, refer to the SAP Security Patch Day portal.

Workarounds

• Restrict access to the vulnerable function module by modifying authorization objects
• Implement firewall rules to limit network access to SAP RFC ports (typically 33xx and 48xx)
• Configure SAP Gateway to reject connections from untrusted networks
• Monitor and limit concurrent RFC connections per user
• Consider disabling the vulnerable function module if it is not business-critical until patching is complete

Note: These workarounds are temporary measures. Applying the official security patch from SAP is the recommended remediation.