CVE-2021-21005 : What You Need to Know

Phoenix Contact FL SWITCH SMCS series products in multiple versions are affected by a vulnerability. An attacker can crash the network stack by sending a hand-crafted TCP-Packet with specific settings. This CVE was published on June 23, 2021, and has a CVSS base score of 7.5 (High).

Understanding CVE-2021-21005

This section provides insights into the nature and impact of the vulnerability.

What is CVE-2021-21005?

The vulnerability exists in Phoenix Contact FL SWITCH SMCS series products due to improper handling of certain network packets. Attackers can exploit this flaw to cause a network stack crash, requiring a device reboot.

The Impact of CVE-2021-21005

The vulnerability poses a high risk to affected systems, with a CVSS base score of 7.5 (High) and an availability impact. It allows attackers to disrupt network operations and potentially lead to denial of service.

Technical Details of CVE-2021-21005

This section dives into the technical aspects of the vulnerability.

Vulnerability Description

When an attacker sends a specially crafted TCP packet with specific flags set, the network stack in Phoenix Contact FL SWITCH SMCS series products crashes, necessitating a device reboot.

Affected Systems and Versions

Various models of Phoenix Contact FL SWITCH SMCS series products up to version 4.70 are impacted by this vulnerability. Products such as FL SWITCH SMCS 16TX, SMCS 14TX/2FX, SMCS 8GT, and more are affected.

Exploitation Mechanism

By exploiting a race condition through concurrent execution using shared resources without proper synchronization, attackers can trigger the vulnerability in the affected Phoenix Contact devices.

Mitigation and Prevention

Protecting and securing systems against CVE-2021-21005 is crucial to prevent network disruptions and unauthorized access.

Immediate Steps to Take

Phoenix Contact recommends operating network-capable devices in closed networks or behind suitable firewalls to mitigate the risk of exploitation.

Long-Term Security Practices

Implementing security best practices, such as regular security assessments, network segmentation, and maintaining up-to-date cybersecurity measures, can enhance the overall security posture.

Patching and Updates

Ensure that affected Phoenix Contact FL SWITCH SMCS series products are updated with the latest patches and firmware releases to address the vulnerability and strengthen system defenses.