### [CVE-2021-21005](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21005)
![](https://img.shields.io/static/v1?label=Product&message=FL%20NAT&color=blue)
![](https://img.shields.io/static/v1?label=Product&message=FL%20SWITCH&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=SMCS%2016TX%20(2700996)%3C%3D%204.70%20&color=brighgreen)
![](https://img.shields.io/static/v1?label=Version&message=SMN%208TX%20(2989365)%3C%3D%204.63%20&color=brighgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=CWE-362%20Race%20Condition%20(Concurrent%20Execution%20using%20Shared%20Resource%20with%20Improper%20Synchronization)&color=brighgreen)

### Description

In Phoenix Contact FL SWITCH SMCS series products in multiple versions if an attacker sends a hand-crafted TCP-Packet with the Urgent-Flag set and the Urgent-Pointer set to 0, the network stack will crash. The device needs to be rebooted afterwards.

### POC

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

#### Github
No PoCs found on GitHub currently.