CVE-2021-25663

8.7 HIGH 2% exploit odds Fix listed

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of service disruption.
Exploit odds: 1.9% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2021-04-22 21:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 03:42 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 1.9% in the next 30 days (EPSS).
Severity: 8.7 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2021-04-22 21:15 UTC
Last modified: 2026-06-17 03:42 UTC
Exploit probability: 1.9% · EPSS, next 30 days
Weakness: CWE-835
Record status: Modified

Affected

Siemens Capital Vstar
Siemens Nucleus Net
Siemens Nucleus Readystart < 4.1.0
Siemens Nucleus Source Code
Siemens Nucleus Readystart < 2017.02.4

Attack profile CVSS 4.0 · 8.7

Attack vector: Network
Complexity: Low
Attack requirements: None
Privileges needed: None
User interaction: None
Confidentiality: None
Integrity: None
Availability: High

Raw vector

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

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-25663.md and follow it. Check whether this project is affected by CVE-2021-25663. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record