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CVE-2021-31884

29
FAUCET Score

CVE-2021-31884 describes a critical vulnerability in numerous Siemens APOGEE, Desigo, and TALON building automation systems, as well as products utilizing Nucleus NET and Nucleus ReadyStart V3. The flaw stems from the DHCP client's assumption of NULL-terminated data in the "Hostname" DHCP option, potentially leading to out-of-bounds reads, writes, and denial-of-service conditions. With a CVSS score of 9.8 (CRITICAL), this vulnerability is remotely exploitable with low attack complexity and no user interaction, allowing for high impact on confidentiality, integrity, and availability. Currently, there is no public exploit code available, nor is there evidence of active exploitation or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:a:siemens:capital_vstar:-:*:*:*:*:*:*:*
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_net:*:*:*:*:*:*:*:*
< 2017.02.1CPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_readystart_v3:*:*:*:*:*:*:*:*
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_source_code:*:*:*:*:*:*:*:*
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:o:siemens:apogee_modular_building_controller_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.45%
Probability of exploitation in next 30 days
EPSS Percentile
70.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0145 is in the 57th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cert-portal.siemens.com / productcert/pdf/ssa-044112.pdf
Vendor Advisory
cert-portal.siemens.com / productcert/pdf/ssa-114589.pdf
Vendor Advisory
cert-portal.siemens.com / productcert/pdf/ssa-620288.pdf
Vendor Advisory