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Cisco NX-OS Software Remote Management Memory Leak Denial of Service Vulnerability

cisco-sa-20190828-nxos-memleak-dos · High · Published · Updated

A vulnerability in the Virtual Shell (VSH) session management for Cisco NX-OS Software could allow an authenticated, remote attacker to cause a VSH process to fail to delete upon termination. This can lead to a build-up of VSH processes that overtime can deplete system memory. When there is no system memory available, this can cause unexpected system behaviors and crashes. The vulnerability is due to the VSH process not being properly deleted when a remote management connection to the device is disconnected. An attacker could exploit this vulnerability by repeatedly performing a remote management connection to the device and terminating the connection in an unexpected manner. A successful exploit could allow the attacker to cause the VSH processes to fail to delete, which can lead to a system-wide denial of service (DoS) condition. The attacker must have valid user credentials to log in to the device using the remote management connection. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190828-nxos-memleak-dos This advisory is part of the August 2019 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication, which includes five Cisco Security Advisories that describe five vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: August 2019 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.

Cisco advisory ·CSAF JSON

Workarounds

There are no workarounds that address this vulnerability.
Mitigation for Cisco NX-OS Software—Configure a VTY Access Class
On some platforms that are running Cisco NX-OS Software, it is possible to limit exposure of an affected device by creating a vty access control list (ACL) on the device and configuring the ACL to permit only known, trusted devices to connect to the device via Telnet and Secure Shell (SSH).

This mitigation is not available on some platforms that are running Cisco NX-OS and should be used only where applicable.

There is no Cisco UCS mitigation that addresses this vulnerability.

The ACL in this example is for IPv4. This vulnerability can also be exploited against IPv6 interfaces. If the NX-OS device is configured for IPv6, the same ACL should be configured for the IPv6 address range.

The following example shows an ACL that permits access to vtys from the 192.168.1.0/24 netblock and the single IP address 172.16.1.2 while denying access from all other addresses:

ip access-list vtyacl
10 permit tcp 192.168.1.0/24 172.16.1.2/32 line vty access-class vtyacl in

For more information about restricting traffic to vtys, see the Cisco Nexus 7000 Series NX-OS Security Configuration Guide http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/6_x/nx-os/security/configuration/guide/b_Cisco_Nexus_7000_NX-OS_Security_Configuration_Guide__Release_6-x/b_Cisco_Nexus_7000_NX-OS_Security_Configuration_Guide__Release_6-x_chapter_01110.html#task_1452624 . It is considered a best practice for an NX-OS device to have a vty ACL configured. Refer to the Cisco Guide to Securing Cisco NX-OS Software Devices http://www.cisco.com/c/en/us/about/security-center/securing-nx-os.html for additional information about hardening Cisco NX-OS devices.

CVEsCVE-2019-1965
Cisco Bug IDsCSCvi15409, CSCvn50393, CSCvn50443, CSCvn50446, CSCvn52167
CVSS ScoreBase 7.7
Base 7.7 CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Product Names From Source
Cisco Unified Computing System (Managed), Cisco NX-OS Software 6.0(2)A8(1), Cisco NX-OS Software 6.0(2)A8(2), Cisco NX-OS Software 6.0(2)A8(3), Cisco NX-OS Software 6.0(2)A8(4), Cisco NX-OS Software 6.0(2)A8(4a), Cisco NX-OS Software 6.0(2)A8(5), Cisco NX-OS Software 6.0(2)A8(6), Cisco NX-OS Software 6.0(2)A8(7), Cisco NX-OS Software 6.0(2)A8(7a), Cisco NX-OS Software 6.0(2)A8(7b), Cisco NX-OS Software 6.0(2)A8(8), Cisco NX-OS Software 6.0(2)A8(9), Cisco NX-OS Software 6.0(2)A8(10a), Cisco NX-OS Software 6.0(2)A8(10), Cisco NX-OS Software 7.0(3)F3(1), Cisco NX-OS Software 7.0(3)F3(2), Cisco NX-OS Software 7.0(3)F3(3), Cisco NX-OS Software 7.0(3)F3(3a), Cisco NX-OS Software 7.0(3)F3(4), Cisco NX-OS Software 7.0(3)F3(3c), Cisco NX-OS Software 7.0(3)F3(5), Cisco NX-OS Software 7.0(3)I4(1), Cisco NX-OS Software 7.0(3)I4(2), Cisco NX-OS Software 7.0(3)I4(3), Cisco NX-OS Software 7.0(3)I4(4), Cisco NX-OS Software 7.0(3)I4(5), Cisco NX-OS Software 7.0(3)I4(6), Cisco NX-OS Software 7.0(3)I4(7), Cisco NX-OS Software 7.0(3)I4(8), Cisco NX-OS Software 7.0(3)I4(8a), Cisco NX-OS Software 7.0(3)I4(8b), Cisco NX-OS Software 7.0(3)I4(8z), Cisco NX-OS Software 7.0(3)I4(1t), Cisco NX-OS Software 7.0(3)I4(6t), Cisco NX-OS Software 7.0(3)I5(1), Cisco NX-OS Software 7.0(3)I5(2), Cisco NX-OS Software 7.0(3)I5(3), Cisco NX-OS Software 7.0(3)I5(3a), Cisco NX-OS Software 7.0(3)I5(3b), Cisco NX-OS Software 7.0(3)I6(1), Cisco NX-OS Software 7.0(3)I6(2), Cisco NX-OS Software 7.0(3)I7(1), Cisco NX-OS Software 7.0(3)I7(2), Cisco NX-OS Software 7.0(3)I7(3), Cisco NX-OS Software 7.0(3)I7(3z), Cisco NX-OS Software 7.3(0)D1(1), Cisco NX-OS Software 7.3(0)DX(1), Cisco NX-OS Software 7.3(0)DY(1), Cisco NX-OS Software 7.3(0)N1(1), Cisco NX-OS Software 7.3(0)N1(1b), Cisco NX-OS Software 7.3(0)N1(1a), Cisco NX-OS Software 7.3(1)D1(1), Cisco NX-OS Software 7.3(1)DY(1), Cisco NX-OS Software 7.3(1)N1(1), Cisco NX-OS Software 7.3(2)D1(1), Cisco NX-OS Software 7.3(2)D1(2), Cisco NX-OS Software 7.3(2)D1(3), Cisco NX-OS Software 7.3(2)D1(3a), Cisco NX-OS Software 7.3(2)D1(1d), Cisco NX-OS Software 7.3(2)N1(1), Cisco NX-OS Software 7.3(2)N1(1b), Cisco NX-OS Software 7.3(2)N1(1c), Cisco NX-OS Software 7.3(3)N1(1), Cisco NX-OS Software 8.1(1), Cisco NX-OS Software 8.1(2), Cisco NX-OS Software 8.1(2a), Cisco NX-OS Software 8.1(1a), Cisco NX-OS Software 8.1(1b), Cisco NX-OS Software 8.2(1), Cisco NX-OS Software 8.2(2), Cisco NX-OS Software 8.3(1), Cisco NX-OS Software 8.3(2), Cisco NX-OS Software 7.3(4)N1(1), Cisco NX-OS Software 7.3(4)N1(1a), Cisco NX-OS Software 7.3(3)D1(1), Cisco NX-OS Software 7.0(3)IA7(1), Cisco NX-OS Software 7.0(3)IA7(2), Cisco NX-OS Software 7.0(3)IM7(2), Cisco NX-OS Software, Cisco MDS 9000 Multilayer Directors and Fabric Switches, Cisco Nexus 7000 Series Switches, Cisco Nexus 5000 Series Switches, Cisco Nexus 3000 Series Switches, Cisco Nexus 6000 Series Switches, Cisco Nexus 9000 Series Switches

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