Detect BeyondTrust Remote Support Pre-Auth RCE (CVE-2026-1731) in Elastic Security
Detects exploitation of CVE-2026-1731, a pre-authentication remote code execution vulnerability (CWE-78, OS command injection) in BeyondTrust Remote Support and Privileged Remote Access. CVSS 9.8. Actively exploited in the wild (CISA KEV). Attackers can execute arbitrary OS commands without authentication via crafted HTTP requests to the appliance web interface.
MITRE ATT&CK
Elastic Detection Query
sequence by host.name with maxspan=5m
[process where process.parent.name : ("bomgar*", "beyondtrust*", "remote_support*", "rs_app*", "pra*")
and process.name : ("cmd.exe", "powershell.exe", "sh", "bash", "python*", "wget", "curl", "nc", "ncat", "whoami", "id")]
[any where
(event.category == "network" and destination.port not in (80, 443, 8080, 8443) and destination.ip != null)
or
(event.category == "file" and file.path : ("/tmp/*", "C:\\Windows\\Temp\\*", "C:\\Users\\*\\AppData\\Local\\Temp\\*"))
]EQL sequence detection: identifies a BeyondTrust parent process spawning a suspicious shell or utility binary, followed within 5 minutes by an anomalous outbound network connection or suspicious file drop — characteristic of post-exploitation after CVE-2026-1731 pre-auth RCE.
Data Sources
Required Tables
False Positives & Tuning
- BeyondTrust update routines that download patches via curl or wget to temp directories
- Legitimate administrative health-check scripts spawned by the appliance service account
- Security tooling that injects into appliance processes for DLP or DRM monitoring purposes
Other platforms for CVE-2026-1731
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 1CVE-2026-1731 PoC HTTP Request Simulation
Expected signal: IIS/nginx access log entry: POST /api/unauthenticated/session with user-agent 'CVE-2026-1731-PoC-Test' and POST body containing ';id;whoami;'. WAF should log or block the request.
- Test 2BeyondTrust Service Account Spawning Shell (Simulated Post-Exploitation)
Expected signal: Windows Security Event 4688: new process cmd.exe with parent process belonging to BeyondTrust service account (btrs_service). Process command line contains whoami, hostname, ipconfig, net user.
- Test 3BeyondTrust Process Outbound Reverse Shell Simulation
Expected signal: Linux auditd execve syscall: bash -i spawned by beyondtrust service process. Network connection record: beyondtrust process connecting outbound to LAB_ATTACKER_IP:4444 (non-standard port, external IP).
References (5)
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