Is CVE-2021-25663 in the CISA KEV catalog?

No. CVE-2021-25663 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-25663?

CVE-2021-25663 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2021-25663?

CVE-2021-25663 has an EPSS score of 1.88% (77th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-25663?

Upgrade nucleus readystart to 2017.02.4 or later.

CVE & CISA-KEV Catalog

CVE-2021-25663

HIGHEPSS 77th pctl

7.5

CVSS v3

NVD

Description

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions < V2303), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.4), Nucleus ReadyStart V4 (All versions < V4.1.0), Nucleus Source Code (All versions including affected IPv6 stack). The function that processes IPv6 headers does not check the lengths of extension header options, allowing attackers to put this function into an infinite loop with crafted length values.

CWE-835

How to fix

Remediation Available

nucleus readystartNVD

Affected:< 2017.02.4Fixed in:2017.02.4CVE-2021-25663derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

1.88%probability of exploitation in 30 days

77thpercentile

Elevated risk: more likely to be exploited than 77% of all known CVEs.

References

Vendor Advisory1

cert-portal.siemens.com

Third-Party Advisory1

us-cert.cisa.gov

Other references1

cert-portal.siemens.com

Related Vulnerabilities

Other CWE-835 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-13935	High	7.5	88%	-	Fix
CVE-2020-36227	High	7.5	78%	-	Fix
CVE-2022-0778	High	7.5	71%	-	Fix
CVE-2019-14241	High	7.5	70%	-	-
CVE-2017-16944	High	7.5	63%	-	Fix
CVE-2024-20353	High	8.6	63%	KEV	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-03-11.