CVE Alert: CVE-2011-20002 – Siemens – SIMATIC S7-1200 CPU V1 family (incl. SIPLUS variants)

Risk verdict

High risk of authentication bypass via capture-replay between engineering software and S7-1200 controllers; no confirmed public exploit is indicated at this time.

Why this matters

If an attacker can replay recorded commands (including critical operations), they could disrupt or stop processes, causing downtime, safety risks, and potential regulatory or financial impacts. The issue targets engineering pathways, so downtime in industrial environments can translate to production delays and equipment wear.

Most likely attack path

An attacker would need access to the same network path used by engineering software and PLCs (no user interaction or privileges required). Once observed traffic is captured, previously valid commands could be replayed to force undesired states (e.g., STOP) without credentials. The gap arises in untrusted or unencrypted on-path communications, enabling manipulation without altering credentials.

Who is most exposed

Facilities employing Siemens SIMATIC S7-1200 systems with engineering workstations connected across plant networks are most at risk, especially where remote access or VPN-linked tooling exposes the engineering path.

Detection ideas

• Replayed or identical command sequences observed at unusual intervals.
• Sudden state changes in controllers without corresponding legitimate inputs.
• Anomalies in engineering software traffic patterns or timing gaps.
• Logs showing successful commands that violate normal workflow order.
• Unusual lack of authentication prompts on critical PLC commands.

Mitigation and prioritisation

• Apply firmware/software upgrade to the affected family (2.0.2 or later) per vendor guidance; verify compatibility in a test environment.
• Tighten network segmentation: limit engineering workstations to PLC subnets; enforce encrypted, authenticated channels.
• Implement mutual authentication between engineering tools and controllers; disable unverified sessions.
• Monitor for replay-like traffic and implement anomaly detection on command sequences.
• Schedule change-management steps: test, back-ups, and rollback plans before production deployment. If exploitation indicators or EPSS-like signals emerge, treat as priority 1.