CVE-2021-27597
📋 TL;DR
CVE-2021-27597 is a denial-of-service vulnerability in SAP NetWeaver AS for ABAP RFC Gateway caused by improper input validation in the memmove() method. Unauthenticated attackers can send specially crafted packets over the network to crash affected systems, rendering them unavailable without data compromise. Organizations running vulnerable SAP NetWeaver versions are affected.
💻 Affected Systems
- SAP NetWeaver AS for ABAP RFC Gateway
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system unavailability affecting business operations, requiring system restart and causing service disruption.
Likely Case
Service disruption through system crashes, leading to downtime and operational impact.
If Mitigated
Minimal impact if systems are patched, network-restricted, or behind proper security controls.
🎯 Exploit Status
Attack requires network access to RFC Gateway port (typically 3300-3301). No authentication needed. The vulnerability is in a core memory handling function.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply SAP Security Note 3020209
Vendor Advisory: https://launchpad.support.sap.com/#/notes/3020209
Restart Required: Yes
Instructions:
1. Download SAP Security Note 3020209 from SAP Support Portal. 2. Apply the kernel patch according to SAP standard procedures. 3. Restart affected SAP systems. 4. Verify patch application through transaction SM51.
🔧 Temporary Workarounds
Network Restriction
allRestrict network access to RFC Gateway ports (3300-3301) to trusted sources only.
Use firewall rules to limit access to RFC ports from authorized IPs only
RFC Gateway Configuration
allConfigure RFC Gateway to use secure settings and limit exposure.
Review and harden RFC Gateway parameters in transaction SMGW
🧯 If You Can't Patch
- Implement strict network segmentation and firewall rules to block unauthorized access to RFC Gateway ports
- Monitor system logs for crash events and implement rapid response procedures for system restarts
🔍 How to Verify
Check if Vulnerable:
Check kernel version via transaction SM51 or command 'disp+work -version'. Compare against affected versions list.Check Version:
disp+work -version (Unix/Linux) or sapevt.exe (Windows)Verify Fix Applied:
Verify SAP Note 3020209 is applied via transaction SNOTE or check kernel patch level in SM51.📡 Detection & Monitoring
Log Indicators:
- System crash dumps
- RFC Gateway error messages
- ABAP dump analysis (ST22)
Network Indicators:
- Unusual traffic to RFC Gateway ports (3300-3301)
- Malformed RFC packets
SIEM Query:
source="sap_system" AND (event_type="system_crash" OR message="*memmove*" OR port=3300 OR port=3301)