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CVE-2021-1523 : Security Advisory and Response

Know about CVE-2021-1523 affecting Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) Mode. Learn the impact, technical details, and mitigation steps.

A vulnerability in Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) Mode could allow an unauthenticated, remote attacker to cause a queue wedge on a leaf switch, resulting in critical control plane traffic being dropped. This could lead to leaf switches being removed from the fabric. Here's what you need to know about CVE-2021-1523 and its implications.

Understanding CVE-2021-1523

Cisco Nexus 9000 Series Fabric Switches ACI Mode Queue Wedge Denial of Service Vulnerability

What is CVE-2021-1523?

The vulnerability in Cisco Nexus 9000 Series Fabric Switches in ACI Mode allows an attacker to disrupt critical control plane traffic, potentially leading to a denial of service (DoS) condition where leaf switches become unavailable.

The Impact of CVE-2021-1523

Exploiting this vulnerability could result in dropping control plane traffic, causing a DoS scenario where leaf switches are no longer accessible within the fabric.

Technical Details of CVE-2021-1523

Here are the technical specifics of the vulnerability:

Vulnerability Description

The issue arises from the mishandling of ingress TCP traffic to a specific port, allowing an attacker to send a stream of TCP packets to disrupt the switch's operation.

Affected Systems and Versions

Cisco NX-OS System Software in ACI Mode is affected by this vulnerability.

Exploitation Mechanism

An attacker can exploit the vulnerability by sending malicious TCP packets to a specific port on a Switched Virtual Interface (SVI) configured on the device.

Mitigation and Prevention

Understanding how to mitigate and prevent the exploitation of CVE-2021-1523 is crucial for network security.

Immediate Steps to Take

If you suspect exploitation, it is recommended to power-cycle the affected device to recover from the vulnerability.

Long-Term Security Practices

Implement robust network security measures to detect and prevent unauthorized access and malicious activities.

Patching and Updates

Stay informed about security updates and patches provided by Cisco to address vulnerabilities like CVE-2021-1523.

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