CVE Alert: CVE-2011-20001 – Siemens – SIMATIC S7-1200 CPU V1 family (incl. SIPLUS variants)

Risk verdict

High risk: unauthenticated remote denial‑of‑service via the affected device web interface could disrupt operations; escalate to priority 1 if threat intel or exploit indicators (e.g., KEV/SSVC exploitation state, EPSS) confirm active exploitation.

Why this matters

For industrial deployments, a DoS on the device’s web interface can halt production lines, trigger safety interlocks, and complicate maintenance windows. With no user interaction or privileges required, an attacker could repeatedly saturate the interface from the network, aiming to service disruption or visibility masking of other intrusions.

Most likely attack path

Attacker needs low-bar network access to the device’s web server; they can send malformed HTTP traffic at high rate to force stop/defect states. No credentials or user interaction are required, and the impact remains on availability (Scope unchanged). The attack relies on unauthenticated access and simple traffic manipulation rather than complex exploitation.

Who is most exposed

Typically exposed in environments where management interfaces are reachable from the plant network or through dedicated remote access paths; common in OT/ICS deployments with limited segmentation or where web interfaces are left accessible for maintenance.

Detection ideas

• Sudden spikes in device CPU or availability loss coinciding with bursts of malformed HTTP traffic
• Logs showing repeated 4xx/5xx HTTP errors from a small number of sources
• Unusual stop/defect state events or watchdog resets
• Anomalous or persistent connectivity attempts to the device’s web interface
• IDS/IPS alerts for abnormal HTTP traffic patterns to management endpoints

Mitigation and prioritisation

• Apply vendor patch to address input handling (target version ≥ V2.0.3 where available)
• If patching isn’t feasible, restrict web interface access to a tightly controlled management network; implement firewall or ACLs and rate limiting
• Deploy a web application firewall or network IDS to filter malformed HTTP requests; monitor for pattern-based attacks
• Consider temporary disablement of the web interface or alternative management methods if exposure cannot be safely mitigated
• Change-management: verify patch/testing, schedule ahead of production windows; if KEV true or EPSS ≥ 0.5, treat as priority 1