What’s Vulnerable › Vulnerabilities

CVE-2021-31889

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-11-09 · updated 2026-06-17
• Weakness: CWE-191

Description

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions < V2303), PLUSCONTROL 1st Gen (All versions), SIMOTICS CONNECT 400 (All versions < V0.5.0.0). Malformed TCP packets with a corrupted SACK option leads to Information Leaks and Denial-of-Service conditions. (FSMD-2021-0015)

Affected products

• Siemens Apogee Modular Building Controller Firmware: all versions
• Siemens Apogee Modular Equiment Controller Firmware: all versions
• Siemens Apogee Pxc Compact Firmware: all versions
• Siemens Apogee Pxc Modular Firmware: all versions
• Siemens Capital VSTAR: all versions
• Siemens Nucleus NET: all versions
• Siemens Nucleus ReadyStart V3: before 2017.02.3 — fixed in 2017.02.3
• Siemens Nucleus Source Code: all versions
• Siemens Talon Tc Compact Firmware: all versions
• Siemens Talon Tc Modular Firmware: all versions

How to fix

Upgrade to a fixed version: Siemens Nucleus ReadyStart V3 2017.02.3. Check the vendor advisory for mitigations.

References

• https://cert-portal.siemens.com/productcert/html/ssa-044112.html
• https://cert-portal.siemens.com/productcert/html/ssa-114589.html
• https://cert-portal.siemens.com/productcert/html/ssa-223353.html
• https://cert-portal.siemens.com/productcert/html/ssa-620288.html
• https://cert-portal.siemens.com/productcert/html/ssa-845392.html
• https://cert-portal.siemens.com/productcert/pdf/ssa-044112.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-114589.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-223353.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-620288.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-845392.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-044112.pdf
• https://cert-portal.siemens.com/productcert/pdf/ssa-114589.pdf

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