# Infinite loop in Siemens Capital Embedded AR Classic 431-422 and others

CVE record · `CVE-2021-25663`

- **Identifiers:** `CVE-2021-25663`
- **State:** Confirmed
- **Severity:** CVSS 8.7 High
- **Critical:** No
- **CNA:** siemens
- **Weakness (CWE):** [CWE-835](https://cwe.mitre.org/data/definitions/835.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Technologies:** [Siemens Capital Embedded AR Classic 431-422](https://agentprime.io/advisories/technology/siemens-capital-embedded-ar-classic-431-422.md) · [Siemens Capital Embedded AR Classic R20-11](https://agentprime.io/advisories/technology/siemens-capital-embedded-ar-classic-r20-11.md) · [Siemens Nucleus NET](https://agentprime.io/advisories/technology/siemens-nucleus-net.md) · [Siemens Nucleus ReadyStart V3](https://agentprime.io/advisories/technology/siemens-nucleus-readystart-v3.md) · [Siemens Nucleus ReadyStart V4](https://agentprime.io/advisories/technology/siemens-nucleus-readystart-v4.md) · [Siemens Nucleus Source Code](https://agentprime.io/advisories/technology/siemens-nucleus-source-code.md)
- **Published:** 22 Apr 2021
- **Updated:** 11 Mar 2025
- **Reviewed by a person:** No

Published by the CVE Program (CNA: siemens) at 22 Apr 2021, 20:42 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

## Affected products, as the CNA wrote them

- Vendor: Siemens. Product: Capital Embedded AR Classic 431-422.
  - affected: `before *` (custom)
  - Other versions: unknown
- Vendor: Siemens. Product: Capital Embedded AR Classic R20-11.
  - affected: `before V2303` (custom)
  - Other versions: unknown
- Vendor: Siemens. Product: Nucleus NET.
  - affected: `All versions`
  - Other versions: unknown
- Vendor: Siemens. Product: Nucleus ReadyStart V3.
  - affected: `before V2017.02.4` (custom)
  - Other versions: unknown
- Vendor: Siemens. Product: Nucleus ReadyStart V4.
  - affected: `before V4.1.0` (custom)
  - Other versions: unknown
- Vendor: Siemens. Product: Nucleus Source Code.
  - affected: `before *` (custom)
  - Other versions: unknown

## Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

## Severity and exploitation

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C`, from CNA (siemens)
- 8.7 High, CVSS 4.0: `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`, from CNA (siemens) (used for this record)

- **CISA KEV:** Not listed.
- **EPSS:** 0.019, the 79th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the CVE Program, published 22 Apr 2021. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2021-25663](https://www.cve.org/CVERecord?id=CVE-2021-25663)
- [NVD: CVE-2021-25663](https://nvd.nist.gov/vuln/detail/CVE-2021-25663)

### References from the CNA

- <https://cert-portal.siemens.com/productcert/pdf/ssa-248289.pdf>
- <https://us-cert.cisa.gov/ics/advisories/icsa-21-103-05> (confirm)
- <https://cert-portal.siemens.com/productcert/html/ssa-248289.html>

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.

## Check whether this affects you

This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it. Compare the affected versions above with what you run.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), `get_advisory` returns this record and `search_advisories` finds related ones. Setup: <https://agentprime.io/mcp.md>
- As JSON: <https://api.agentprime.io/v1/advisories/CVE-2021-25663>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2021-25663/>. Everything for agents: <https://agentprime.io/llms.txt>.