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CVE-2021-31889

28
FAUCET Score

CVE-2021-31889 is a critical vulnerability affecting several Siemens products, including Capital Embedded AR Classic, PLUSCONTROL 1st Gen, and SIMOTICS CONNECT 400. This flaw allows an unauthenticated attacker to trigger information leaks and denial-of-service conditions by sending malformed TCP packets with a corrupted SACK option. With a CVSS score of 9.1, it presents a high risk due to its network-based attack vector and low attack complexity. Currently, there is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:a:siemens:capital_vstar:*:*:*:*:*:*:*:*
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_net:*:*:*:*:*:*:*:*
< 2017.02.3CPE 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

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.11%
Probability of exploitation in next 30 days
EPSS Percentile
79.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0211 is in the 69th 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/html/ssa-044112.html
cert-portal.siemens.com / productcert/html/ssa-114589.html
cert-portal.siemens.com / productcert/html/ssa-223353.html
cert-portal.siemens.com / productcert/html/ssa-620288.html
cert-portal.siemens.com / productcert/html/ssa-845392.html
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-223353.pdf
cert-portal.siemens.com / productcert/pdf/ssa-620288.pdf
cert-portal.siemens.com / productcert/pdf/ssa-845392.pdf