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PatchSiren cyber security CVE debrief

CVE-2024-43647 Siemens CVE debrief

A vulnerability in Siemens SIMATIC S7-200 SMART CPU devices allows unauthenticated remote attackers to cause denial of service by sending malformed TCP packets. The flaw stems from improper handling of TCP packets with incorrect structure. Recovery requires physical intervention—unplugging and re-plugging the network cable. Siemens has stated that no fix is currently planned for this vulnerability. The affected product line includes 18 CPU variants across CR, SR, and ST series. Given the CVSS 7.5 HIGH severity and network-based attack vector without authentication requirements, organizations should prioritize network segmentation and access controls as compensating controls.

Vendor
Siemens
Product
SIMATIC S7-200 SMART CPU CR40 (6ES7288-1CR40-0AA0)
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2024-09-10
Original CVE updated
2024-09-10
Advisory published
2024-09-10
Advisory updated
2024-09-10

Who should care

Organizations operating Siemens SIMATIC S7-200 SMART CPU devices in industrial control environments, particularly those with network-connected PLCs. Critical infrastructure operators, manufacturing facilities, and water/wastewater utilities using this hardware should assess exposure. Security architects designing OT network segmentation and incident response teams supporting industrial environments need to prioritize compensating controls given the absence of a planned patch.

Technical summary

The vulnerability exists in the TCP stack implementation of Siemens SIMATIC S7-200 SMART CPU devices. When processing TCP packets with malformed structure, the device fails to handle the error condition gracefully, resulting in a denial of service state. The attack requires no authentication and can be executed remotely over the network. Notably, the device cannot recover automatically from this condition—physical intervention is required to restore operations by disconnecting and reconnecting the network cable. This indicates a failure mode that crashes or hangs the network interface processor rather than triggering a watchdog reset.

Defensive priority

high

Recommended defensive actions

  • Implement network segmentation to isolate affected SIMATIC S7-200 SMART CPU devices from untrusted networks and the internet
  • Restrict network access to trusted users and systems only through firewall rules and access control lists
  • Monitor network traffic for anomalous TCP packet patterns targeting industrial control systems
  • Establish physical access procedures to enable rapid network cable reset if denial of service occurs
  • Consider deploying industrial intrusion detection systems to detect and block malformed TCP packets before reaching affected devices
  • Review and apply CISA ICS recommended practices for defense-in-depth strategies
  • Document and test incident response procedures for physical recovery of affected devices
  • Evaluate replacement or upgrade paths for affected hardware given no fix is planned

Evidence notes

CVE published 2024-09-10 per CISA CSAF advisory ICSA-24-261-01. CVSS 3.1 vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H confirms network-based, unauthenticated, high-availability-impact attack. Vendor explicitly states 'no fix planned' in remediation guidance. Physical recovery action (network cable reset) documented in source advisory.

Official resources

2024-09-10