CVE-2021-25663

Name: CVE-2021-25663
Creator: NVD / NIST
Published: 2021-04-22T21:15:09.957+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.7/10EPSS 1.88%

Last modified Jun 17, 2026

CVE-2021-25663 is a high-severity vulnerability rated 8.7/10 on the CVSS scale. 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.. EPSS estimates a 1.88% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

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

CVSS 4.0

8.7/10

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

EPSS Probability

1.88%

76.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Siemens	Capital Vstar	All versions
Siemens	Nucleus Net	All versions
Siemens	Nucleus Readystart	< 4.1.0
Siemens	Nucleus Source Code	All versions
Siemens	Nucleus Readystart	< 2017.02.4

References

https://cert-portal.siemens.com/productcert/html/ssa-248289.html
https://cert-portal.siemens.com/productcert/pdf/ssa-248289.pdfVendor Advisory
https://us-cert.cisa.gov/ics/advisories/icsa-21-103-05Third Party Advisory, US Government Resource
https://cert-portal.siemens.com/productcert/html/ssa-248289.html
https://cert-portal.siemens.com/productcert/pdf/ssa-248289.pdfVendor Advisory
https://us-cert.cisa.gov/ics/advisories/icsa-21-103-05Third Party Advisory, US Government Resource

Timeline

Published: Apr 22, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-25663?

How severe is CVE-2021-25663?

CVE-2021-25663 has a CVSS score of 8.7/10 (HIGH severity). The EPSS model estimates a 1.88% probability of exploitation in the next 30 days.

How do I fix CVE-2021-25663?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-25663?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST