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AUSCERT External Security Bulletin Redistribution
Cisco Nexus and Cisco Multilayer Director Switches MOTD
Telnet Login Reset Vulnerability
12 June 2015
AusCERT Security Bulletin Summary
Product: Cisco Nexus
Cisco Multilayer Director Switches
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2015-0775
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Cisco Nexus and Cisco Multilayer Director Switches MOTD Telnet Login Reset
Threat Type: CWE-399: Resource Management Errors
IntelliShield ID: 39280
First Published: 2015 June 10 19:29 GMT
Last Published: 2015 June 10 19:29 GMT
Port: Not available
Urgency: Possible use
Severity: Mild Damage
CVSS Base: 5.0
CVSS Version 2.0
CVSS Temporal: 4.8
Version Summary: Cisco Nexus and Cisco Multilayer Director Switches contain a
vulnerability that could allow an unauthenticated, remote attacker to cause a
denial of service condition. Software updates are not available.
A vulnerability in the Message of the Day (MOTD) or banner functionality of
the NX-OS Software could allow an unauthenticated, remote attacker to cause
the login process to reset.
The vulnerability is due to the MOTD display handling when a certain type of
terminal session is requested via Telnet. An attacker could exploit this
vulnerability by repeatedly issuing a Telnet session to the NX-OS device,
causing the login process to reset. An exploit could allow the attacker to
cause the login process of the NX-OS device to reset repeatedly.
Cisco has confirmed the vulnerability; however, software updates are not
The following Cisco Nexus and Cisco Multilayer Director Switches running the
following releases of Cisco NX-OS Software are affected.
Cisco Nexus 5000 Series Switches running NX-OS Software release
Cisco Nexus 7000 Series Switches running NX-OS Software release 6.2(12)
Cisco MDS 9000 Series Multilayer Switches running NX-OS Software release
Cisco Nexus 9000 Series Switches running NX-OS Software release 7.0(3)
Cisco Nexus 3000 Series Switches running NX-OS Software release
Cisco Nexus 4000 Series Switches running NX-OS Software release
Cisco Nexus 1000V Switches running NX-OS Software release 5.2(1)SV3(2.1)
To exploit this vulnerability, an attacker would need to start a Telnet
session with the targeted device. This requirement may decrease the likelihood
of a successful exploit depending on how the targeted device is configured.
Cisco indicates through the CVSS score that functional exploit code exists;
however, the code is not known to be publicly available.
Cisco has released bug IDs CSCuo10554, CSCuu75466, CSCuu75471, CSCuu75484,
CSCuu75498, CSCuu77182, and CSCuu77170 for registered users, which contain
additional details and an up-to-date list of affected product versions.
An unauthenticated, remote attacker could exploit this vulnerability to cause
the login process on an affected device to reset repeatedly, resulting in a
denial of service (DoS) condition.
The vulnerability is due to improper handling of the MOTD display when a
certain type of terminal session is requested via Telnet.
An unauthenticated, attacker could exploit this vulnerability by repeatedly
issuing a Telnet session to a targeted device. An exploit could allow the
attacker to cause the login process of the device to reset repeatedly,
resulting in a DoS condition.
Administrators are advised to contact the vendor regarding future updates and
Administrators are advised to allow only trusted users to have network access.
Administrators can help protect affected systems from external attacks by
using a solid firewall strategy.
Administrators may consider using IP-based access control lists (ACLs) to
allow only trusted systems to access the affected systems.
Administrators are advised to monitor affected systems.
Software updates are not available.
The security vulnerability applies to the following combinations of products.
Cisco Cisco NX-OS Software for Nexus 3000 Series 7.2(0)ZN(99.67) | for Nexus
4000 Series 4.1(2)E1(1f) | for Nexus 5000 Series 6.0(2)N2(2) | for Nexus 7000
Series 6.2(12) | for Nexus 9000 Series 7.0(3)
Cisco Cisco MDS 9000 NX-OS Software 6.2 (11)
Cisco Cisco Nexus 1000V Switch 5.2(1)SV3(2.1) Base
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