Two vulnerabilities in the Cisco IOx application environment of Cisco 809 and 829 Industrial ISRs and Cisco CGR1000 devices that are running Cisco IOS Software could allow an attacker to cause a DoS condition or execute arbitrary code with elevated privileges on an affected device.
These vulnerabilities reside in either the ingress packet processing functionality or the implementation of the inter-VM communication channel of Cisco IOS Software for the affected products.
The vulnerabilities are not dependent on one another; exploitation of one of the vulnerabilities is not required to exploit the other vulnerability.
Details about the vulnerabilities are as follows.
Cisco IOx Application Environment for IOS Software for Cisco Industrial Routers Remote Code Execution Vulnerability
A vulnerability in the implementation of the inter-VM communication channel of Cisco IOS Software for Cisco 800 Series Industrial ISRs and Cisco CGR1000 devices could allow an authenticated, local attacker to execute arbitrary code on an affected system with high privileges.
The vulnerability is due to incorrect bounds checking of certain type, length, value (TLV) fields of signaling packets that are exchanged between Cisco IOS Software and Guest OS. An attacker could exploit this vulnerability by authenticating to the device by using low-privileged-user credentials and then sending crafted signaling packets while establishing a TCP session destined to the process that manages the inter-VM communication of an affected device. When the packets are processed, an exploitable buffer overflow condition may occur. A successful exploit could allow the attacker to execute arbitrary code in the context of the Cisco IOS Software VM running on an affected device.
This vulnerability can be exploited by using malicious TCP packets over either IPv4 or IPv6.
Bug ID(s): CSCvr15042
CVE ID: CVE-2020-3257
Security Impact Rating (SIR): High
CVSS Base Score: 7.8
CVSS Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Mitigation for CVE-2020-3257
Customers who do not use Guest OS can disable the virtual interface that is managed by Cisco IOS Software. This interface provides connectivity between the Cisco IOS Software VM and Guest OS. Configuring the virtual interface in shutdown mode eliminates the attack vector for this vulnerability and may be a suitable mitigation until affected devices can be upgraded. Applying this mitigation will prevent further access to Guest OS.
The following table identifies the virtual interface for each affected Cisco product:
|809 Industrial ISRs
|Gigabit Ethernet 2
|829 Industrial ISRs
|Gigabit Ethernet 5
|Gigabit Ethernet 0/1
Administrators can configure the interface in shutdown mode by entering the shutdown command in interface configuration mode. The following example shows the output of the show run interface gigabitEthernet <id> command for a device that has an interface in shutdown mode:
Router#show run interface gigabitEthernet <id> | i shutdown
Cisco IOx Application Environment for IOS Software for Cisco Industrial Routers Guest OS Denial of Service Vulnerability
A vulnerability in the ingress packet processing functionality of Cisco IOS Software for Cisco 809 and 829 Industrial ISRs and Cisco CGR1000 devices could allow an unauthenticated, adjacent attacker to shut down, reload, or uninstall the Guest OS instance running on an affected device, resulting in a DoS condition.
The vulnerability is due to insufficient isolation of an internal, emulated Ethernet interface that should not process traffic from outside the device when the traffic is destined for the 127.0.0.0/8 range. An attacker could exploit this vulnerability by sending malicious IP packets. A successful exploit could allow the attacker to shut down, reload, or uninstall the Guest OS instance running on an affected device.
Bug ID(s): CSCvq68872
CVE ID: CVE-2020-3199
Security Impact Rating (SIR): High
CVSS Base Score: 8.1
CVSS Vector: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Determine Whether Guest OS Is Enabled
Administrators can determine whether Guest OS is enabled on a device by using the show iox host list detail | include OS status command in the device CLI.
The following example shows the output of the command for a device that has Guest OS enabled:
Router#show iox host list detail | include OS status
OS status: RUNNING
If this command does not exist, or if it produces output that does not show the string RUNNING in the OS status field, the device is not affected by this vulnerability.