Detect SolarWinds Serv-U Uncontrolled Resource Consumption (CVE-2026-28318) in Elastic Security
Detects exploitation of CVE-2026-28318, an uncontrolled resource consumption vulnerability (CWE-400) in SolarWinds Serv-U. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog and allows attackers to exhaust server resources, leading to denial of service conditions. Detection focuses on abnormal connection patterns, resource exhaustion indicators, and anomalous request volumes targeting Serv-U services.
MITRE ATT&CK
- Tactic
- Impact
Elastic Detection Query
sequence by destination.ip, destination.port with maxspan=5m
[network where destination.port in (21, 22, 990, 989, 443, 80) and
(process.name like~ "Serv-U*" or destination.port in (21, 990, 989))]
[network where destination.port in (21, 22, 990, 989, 443, 80)] with runs=500Elastic EQL sequence query detecting rapid repeated connections to Serv-U service ports, indicative of resource exhaustion attack. Uses run count to identify connection floods within a 5-minute window.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate enterprise file transfer clients with high-frequency polling
- Monitoring systems that perform frequent health checks against Serv-U endpoints
- Load balancers forwarding many connections from a virtual IP
- Automated deployment pipelines transferring build artifacts via FTP/SFTP
Other platforms for CVE-2026-28318
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Simulated FTP Connection Flood to Serv-U (Linux)
Expected signal: Network flow logs showing 600+ connection attempts from the test host to port 21 of the target within a short window; firewall logs recording SYN flood or connection rate spike; Serv-U application logs showing session limit errors or connection refused messages
- Test 2SFTP Connection Exhaustion via Python (Linux/macOS)
Expected signal: Process telemetry showing python3 spawning ~600 concurrent TCP connections to port 22; network visibility tools showing elevated socket counts; target host showing increased memory/thread usage for ServUDaemon.exe
- Test 3FTPS Connection Exhaustion via hping3 (Linux)
Expected signal: Network IDS/IPS alerts for SYN flood to port 990; firewall logs recording high packet rate from test source IP; Serv-U host showing elevated network interrupt handling load; Windows Performance Monitor showing ServUDaemon.exe handle/connection count spike
References (4)
Unlock Pro Content
Get the full detection package for CVE-2026-28318 including response playbook, investigation guide, and atomic red team tests.