CVE-2019-1594 : Exploit Details and Defense Strategies

A flaw in the implementation of 802.1X for Cisco NX-OS Software could be exploited by an unauthorized attacker to cause a denial of service (DoS) on vulnerable devices.

Understanding CVE-2019-1594

This CVE identifies a vulnerability in Cisco NX-OS Software that could lead to a DoS attack on affected devices.

What is CVE-2019-1594?

The vulnerability stems from inadequate verification of Extensible Authentication Protocol over LAN (EAPOL) frames, allowing an attacker to trigger system-level restarts on devices with 802.1X functionality enabled.

The Impact of CVE-2019-1594

The vulnerability poses a high availability impact, with a CVSS base score of 7.4, indicating a significant threat to affected systems.

Technical Details of CVE-2019-1594

This section delves into the specifics of the vulnerability.

Vulnerability Description

The flaw allows an adjacent attacker to send crafted EAPOL frames, causing multiple restarts of the Layer 2 (L2) forwarding process and ultimately leading to a DoS situation.

Affected Systems and Versions

Nexus 1000V Switch for VMware vSphere: < 5.2(1)SV3(1.4b)
Nexus 3000 Series Switches: < 7.0(3)I7(4)
Nexus 3500 Platform Switches: < 7.0(3)I7(4)
Nexus 2000, 5500, 5600, and 6000 Series Switches: < 7.3(5)N1(1), < 7.1(5)N1(1b)
Nexus 7000 and 7700 Series Switches: < 8.2(3)
Nexus 9000 Series Fabric Switches in ACI Mode: < 13.2(1l)
Nexus 9000 Series Switches in Standalone NX-OS Mode: < 7.0(3)I7(4)

Exploitation Mechanism

By sending a specifically crafted EAPOL frame to a device interface, the attacker can force multiple restarts of the L2 forwarding process, leading to a system-level restart.

Mitigation and Prevention

Protecting systems from this vulnerability requires immediate actions and long-term security practices.

Immediate Steps to Take

Disable 802.1X functionality on vulnerable devices if not essential.
Implement network segmentation to limit the impact of potential attacks.
Monitor network traffic for any suspicious EAPOL frames.

Long-Term Security Practices

Regularly update and patch NX-OS software to mitigate known vulnerabilities.
Conduct security assessments and audits to identify and address potential weaknesses.

Patching and Updates

Apply the necessary patches provided by Cisco to address the vulnerability and enhance system security.