Detect SolarWinds Serv-U Uncontrolled Resource Consumption (CVE-2026-28318) in CrowdStrike LogScale
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
LogScale Detection Query
#event_simpleName=NetworkConnectIP4 OR #event_simpleName=NetworkConnectIP6
| RemotePort IN [21, 22, 990, 989]
| stats count(aid) AS connection_count, dc(RemoteAddressIP4) AS unique_targets BY LocalAddressIP4, RemotePort, aid
OVER last 5 minutes
| where connection_count > 500
| eval severity=if(connection_count > 2000, "CRITICAL", if(connection_count > 1000, "HIGH", "MEDIUM"))
| join aid [
#event_simpleName=ProcessRollup2
| fields aid, FileName, CommandLine, ParentBaseFileName
]
| table LocalAddressIP4, RemotePort, connection_count, unique_targets, FileName, CommandLine, severityCrowdStrike Falcon CQL detecting rapid outbound network connections to Serv-U FTP/SFTP/FTPS ports from endpoint agents. Correlates network events with process context to identify potentially malicious tools generating resource exhaustion traffic.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate FTP client software performing bulk uploads or downloads
- Backup agents establishing many parallel connections to Serv-U
- Internal DevOps tooling that transfers artifacts to Serv-U endpoints
- Vulnerability scanners authorized to test Serv-U availability and response
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)
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