What is the CVSS score of CVE-2021-31884?

CVE-2021-31884 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 1.5%.

Capital Vstar CVE-2021-31884

CRITICAL

Improper Null Termination (CWE-170)

2021-11-09 productcert@siemens.com

9.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-170 OWASP Top 10:2025 A05:2025 - Injection ASVS 5.0 V1 - Encoding and Sanitization Null terminator handling
Impact	CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the critical-severity affected system.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

No patch listed yet 1.5% exploitation probability (EPSS)

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AnalysisAI

A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All versions), APOGEE MEC (PPC) (BACnet) (All versions), APOGEE MEC (PPC) (P2. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified under CWE-170. A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All versions), APOGEE MEC (PPC) (BACnet) (All versions), APOGEE MEC (PPC) (P2 Ethernet) (All versions), APOGEE PXC Compact (BACnet) (All versions < V3.5.4), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.19), APOGEE PXC Modular (BACnet) (All versions < V3.5.4), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.19), Capital VSTAR (All versions with enabled Ethernet options), Desigo PXC00-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC00-U (All versions >= V2.3 and < V6.30.016), Desigo PXC001-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC100-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC12-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC128-U (All versions >= V2.3 and < V6.30.016), Desigo PXC200-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC36.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC50-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC64-U (All versions >= V2.3 and < V6.30.016), Desigo PXM20-E (All versions >= V2.3 and < V6.30.016), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.4), Nucleus Source Code (All versions), TALON TC Compact (BACnet) (All versions < V3.5.4), TALON TC Modular (BACnet) (All versions < V3.5.4). The DHCP client application assumes that the data supplied with the “Hostname” DHCP option is NULL terminated. In cases when global hostname variable is not defined, this may lead to Out-of-bound reads, writes, and Denial-of-service conditions. (FSMD-2021-0014) Affected products include: Siemens Capital Vstar, Siemens Nucleus Net, Siemens Nucleus Readystart V3, Siemens Nucleus Source Code, Siemens Apogee Modular Building Controller Firmware.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.8 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All versions), APOGEE MEC (PPC) (BACnet) (All versions), APOGEE MEC (PPC) (P2 Ethernet) (All versions), APOGEE PXC Compact (BACnet) (All versions < V3.5.4), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.19), APOGEE PXC Modular (BACnet) (All versions < V3.5.4), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.19), Capital VSTAR (All versions with enabled Ethernet options), Desigo PXC00-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC00-U (All versions >= V2.3 and < V6.30.016), Desigo PXC001-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC100-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC12-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC128-U (All versions >= V2.3 and < V6.30.016), Desigo PXC200-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC36.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC50-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC64-U (All versions >= V2.3 and < V6.30.016), Desigo PXM20-E (All versions >= V2.3 and < V6.30.016), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.4), Nucleus Source Code (All versions), TALON TC Compact (BACnet) (All versions < V3.5.4), TALON TC Modular (BACnet) (All versions < V3.5.4). The DHCP client application assumes that the data supplied with the “Hostname” DHCP option is NULL terminated. In cases when global hostname variable is not defined, this may lead to Out-of-bound reads, writes, and Denial-of-service conditions. (FSMD-2021-0014)

Threat Intelligence Overview

EPSS Score

1.5%

Top 30% exploitable

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV No

Public POC No

EPSS 1.5%

Patch available No

Active threat No

Deciding rule

CRITICAL severity

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +1

CVSS: +49

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)NVD

cpe:2.3:a:siemens:capital_vstar:-:*:*:*:*:*:*:*

cpe:2.3:a:siemens:nucleus_net:*:*:*:*:*:*:*:*

cpe:2.3:a:siemens:nucleus_readystart_v3:*:*:*:*:*:*:*:*

cpe:2.3:a:siemens:nucleus_source_code:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:apogee_modular_building_controller_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:apogee_modular_equiment_controller_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:apogee_pxc_compact_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:apogee_pxc_modular_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:talon_tc_compact_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:talon_tc_modular_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc00-e.d_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc00-u_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc001-e.d_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc12-e.d_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc22-e.d_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc22.1-e.d_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc36.1-e.d_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc50-e.d_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc64-u_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:siemens:desigo_pxc100-e.d_firmware:*:*:*:*:*:*:*:*

+ 5 more