CVE-2021-33737: Siemens SIMATIC CP 343-1 Advanced Firmware

High severity, CVSS 7.5. EPSS: 1.1% chance of exploitation in the next 30 days.

A vulnerability has been identified in SIMATIC CP 343-1 (incl. SIPLUS variants) (All versions), SIMATIC CP 343-1 Advanced (incl. SIPLUS variants) (All versions), SIMATIC CP 343-1 ERPC (All versions), SIMATIC CP 343-1 Lean (incl. SIPLUS variants) (All versions), SIMATIC CP 443-1 (All versions < V3.3), SIMATIC CP 443-1 (All versions < V3.3), SIMATIC CP 443-1 Advanced (All versions < V3.3), SIPLUS NET CP 443-1 (All versions < V3.3), SIPLUS NET CP 443-1 Advanced (All versions < V3.3). Sending a specially crafted packet to port 102/tcp of an affected device could cause a denial of service condition. A restart is needed to restore normal operations.

Affected products

• Siemens SIMATIC CP 343-1 Advanced Firmware: any version
• Siemens SIMATIC CP 343-1 Erpc Firmware: any version
• Siemens SIMATIC CP 343-1 Firmware: any version
• Siemens SIMATIC CP 343-1 Lean Firmware: any version
• Siemens SIMATIC CP 443-1 Advanced Firmware: any version
• Siemens SIMATIC CP 443-1 Firmware: any version

Published 2021-09-14. Last modified 2026-06-17.