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CVE-2021-25663

24
FAUCET Score

CVE-2021-25663 is a high-severity vulnerability affecting Siemens Capital Embedded AR Classic and Nucleus products, including Nucleus NET and Nucleus ReadyStart. It stems from an unchecked length value in the IPv6 header processing function, allowing an attacker to trigger an infinite loop via a crafted IPv6 packet. This denial-of-service vulnerability has a CVSS score of 7.5, indicating a network-exploitable attack with low complexity and high availability impact. Currently, there is no evidence of active exploitation, public exploit code, 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:*:*:*:*:*:*:*:*
< 4.1.0CPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_readystart:*:*:*:*:*:*:*:*
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_source_code:-:*:*:*:*:*:*:*
< 2017.02.4CPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_readystart:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

8.7HIGH

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
NONE
VS Integrity
NONE
VS Availability
HIGH
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
1.88%
Probability of exploitation in next 30 days
EPSS Percentile
77.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0188 is in the 61st percentile among its peer group of 51,553 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 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-248289.html
cert-portal.siemens.com / productcert/pdf/ssa-248289.pdf
Vendor Advisory
us-cert.cisa.gov / ics/advisories/icsa-21-103-05
Third Party AdvisoryUS Government Resource