Cisco has rolled out several critical software patches for the CISCO Nexus 7000-series switches and the related NX-OS software.

According to the Cisco Security Advisory, an attacker could exploit the vulnerabilities to gain remote access to vulnerable systems and execute code or commands.

According to Wednesday’s Cisco Security Advisory, both the Nexus 7000 and 7700 series switches are susceptible to overlay transport virtualization buffer overflow flaws (CVE-2016-1453).

“A vulnerability in the Overlay Transport Virtualization (OTV) generic routing encapsulation (GRE) implementation of the Cisco Nexus 7000 and 7700 Series Switches could allow an unauthenticated, adjacent attacker to cause a reload of the affected system or to remotely execute code.” states the CISCO advisory.

This flaw is the result of the “incomplete input validation performed on the size of overlay transport virtualization packet header parameters.”

Cisco has released a software update and workaround to address the flaw and mitigate the risk of exposure.

Cisco Nexus products affected by the vulnerability, when configured to use the OTV functionality, are the Nexus 7000 Series Switches, Nexus 7700 Series Switches.

The OTV functionality was introduced with Cisco NX-OS Software Release 5.0(3) or later for the Nexus 7000 Series, and Cisco NX-OS.

Cisco also released updates to address a critical vulnerability, tracked as CVE-2015-0721, that is related to the Secure Shell (SSH) subsystem of the Cisco Nexus switches. The flaw could be exploited by a remote and authenticated attacker to bypass authentication, authorization, and accounting (AAA) restrictions and execute commands.

“A vulnerability in the SSH subsystem of the Cisco Nexus family of products could allow an authenticated, remote attacker to bypass authentication, authorization, and accounting (AAA) restrictions.” reads the Cisco Advisory.

“An attacker could exploit this vulnerability by authenticating to an affected device and passing a malicious value as part of the login procedure. A successful exploit could allow an attacker to bypass AAA restrictions and execute commands on the device command-line interface (CLI) that should be restricted to a different privileged user role.”

At the time I was writing, Cisco did not provide a workaround for the vulnerability. Less significant were a number of Cisco advisories rated as high; each tied to the company’s NX-OS operating system.

Cisco also addressed a number of flaws rated as “high” severe:

CVE-2016-1454 – Cisco NX-OS Border Gateway Protocol Denial of Service Vulnerability.

“A vulnerability in the Border Gateway Protocol (BGP) implementation of Cisco NX-OS System Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition due to the device unexpectedly reloading. The vulnerability is due to incomplete input validation of the BGP update messages”

For the following DHCPv4 Packet DoS flaws Cisco has released software updates but no workarounds are available.

CVE-2015-6392 -Cisco NX-OS Software Crafted DHCPv4 Packet Denial of Service Vulnerability

“A vulnerability in the implementation of the DHCPv4 relay agent and smart relay agent in Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper validation of crafted DHCPv4 offer packets.”

CVE-2015-6393 – Cisco NX-OS Software Malformed DHCPv4 Packet Denial of Service Vulnerability

“A vulnerability in the implementation of the DHCPv4 relay agent in Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

The vulnerability is due to improper validation of malformed DHCPv4 packets.”

Pierluigi Paganini

(Security Affairs – CISCO Nexus, hacking)

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