Security readout for executives and security teams
Plain-English summary
Older Siemens S7-1200 industrial controllers can be knocked offline by an attacker on the network who floods the device's built-in web page with malformed requests. The controller stops running, which can halt the physical process it controls. No password or login is needed, so any system that can reach the device is a potential attack path.
Executive priority
Plan a maintenance window to update vulnerable S7-1200 V1/V2 CPUs and verify network segmentation around plant floor controllers. Treat as production-availability risk, not data theft.
Technical view
CVE-2011-20001 is a CWE-20 input validation flaw in the integrated web server of Siemens SIMATIC S7-1200 V1 and V2 CPUs (including SIPLUS variants) before V2.0.3. Sending high-rate malformed HTTP traffic causes the CPU to enter a stop/defect state, producing an unauthenticated remote denial of service. CVSS 4.0 score is 8.7 with high availability impact and no confidentiality or integrity impact.
Likely exposure
Exposure is highest for SIMATIC S7-1200 V1/V2 CPUs (including SIPLUS variants) running firmware older than V2.0.3 that have the integrated web server reachable from engineering, IT, or untrusted networks. OT environments without strict cell/zone segmentation face the greatest risk.
Exploitation context
No known exploitation in the wild and not listed in CISA KEV. The vulnerability requires only network reach to the device's web server and a high-rate stream of malformed HTTP traffic; no authentication is needed. No public exploit is cited in the source bundle.
Researcher notes
CWE-20 input validation flaw in the embedded web server's HTTP parsing under high request rates. CVSS 4.0 vector indicates network attack, no privileges, no UI, with high availability impact only (VA:H) and no confidentiality/integrity impact. Despite the CVE-2011 numbering, the record was published 2025-10-14 referencing Siemens SSA-625789. Fixed firmware is V2.0.3. SIPLUS hardened variants share the same firmware and are equally affected. Treat any V1/V2 CPU below V2.0.3 as vulnerable until confirmed patched.
Mitigation direction
- Update affected S7-1200 V1/V2 CPUs to firmware V2.0.3 or later per Siemens SSA-625789.
- Disable the integrated web server on CPUs where it is not operationally required.
- Restrict TCP/80 and TCP/443 access to controllers using firewalls and ACLs.
- Place S7-1200 CPUs inside an ISA/IEC 62443 cell behind a properly configured industrial firewall.
- Consult the Siemens ProductCERT advisory for any model-specific guidance and updates.
Validation and detection
- Inventory all S7-1200 CPUs and record firmware version against the V2.0.3 threshold.
- Identify which CPUs expose ports 80/443 to engineering, IT, or external networks.
- Confirm whether the integrated web server is enabled on each device via TIA Portal configuration.
- Review network captures or IDS logs for anomalous HTTP traffic toward controller IPs.
- Cross-check device models against Siemens SSA-625789 for affected SKUs and SIPLUS variants.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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Open ATT&CK lookupCVE-2011-20001 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.7 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA and ADP enrichment extracted from CVE v5
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CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
8.7HighVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source materials
- CVE List V5 sourceCVE List V5
- https://cert-portal.siemens.com/productcert/html/ssa-625789.htmlCVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.