Cisco Security Advisory
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CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L/E:X/RL:X/RC:X
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A vulnerability in the image verification function of Cisco Expressway Series and Cisco TelePresence Video Communication Server (VCS) could allow an authenticated, remote attacker to execute code with internal user privileges on the underlying operating system.
The vulnerability is due to insufficient validation of the content of upgrade packages. An attacker could exploit this vulnerability by uploading a malicious archive to the Upgrade page of the administrative web interface. A successful exploit could allow the attacker to execute code with user-level privileges (the _nobody account) on the underlying operating system.
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-ewver-c6WZPXRx
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Vulnerable Products
At the time of publication, this vulnerability affected Cisco Expressway Series and Cisco TelePresence VCS if they were running a release earlier than the first fixed release. This vulnerability was introduced when support for validation of SHA512 checksums was introduced in Release X8.8.
For information about affected software releases, see the Fixed Software section of this advisory. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
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There are no workarounds that address this vulnerability.
While the following mitigations have been deployed and were proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.
Firewall Rule Modifications
Access to the management plane of Cisco Expressway Series and Cisco TelePresence VCS should be restricted to trusted networks. Administrators can restrict access to the management ports (HTTPS/SSH) within the firewall rules on the device or by using an external firewall. The web UI port numbers can also be modified in the configuration.
As a best practice, access to the management plane of Cisco Expressway Series and Cisco TelePresence VCS should not be exposed to the internet. For additional information, see the Intrusion Protection section of the Cisco Expressway Administrator Guide.
Dedicated Management Interface
As a best practice, access to the management plane of Cisco Expressway Series and Cisco TelePresence VCS should not be exposed to the internet. Beginning with Release X12.7, the product introduced a Dedicated Management Interface (DMI). Administrators can enable the DMI and implement the following configuration:
- Allow the DMI to be the only interface used for management
- Configure the DMI to be accessed only from trusted segments
For additional information, see Configuring the Dedicated Management Interface (DMI) section of the Cisco Expressway Administrator Guide.
Client Certificate-Based Security
This vulnerability can be exploited only by an authenticated administrator. Using client authentication certificates helps prevent brute forcing of the administrative passwords. For additional information, see the Configuring Certificate-Based Authentication section of the Cisco Expressway Administrator Guide.
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When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories page, to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
Fixed Releases
At the time of publication, Cisco Expressway Series and Cisco TelePresence VCS releases X14.0.3 and later contained the fix for this vulnerability.
For information about fixed software releases, see the Details section in the bug ID(s) at the top of this advisory.
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Cisco recommends that customers upgrade to a fixed software release to address this vulnerability and implement the following best practices:
- Not exposing the management plane to the internet
- Changing all administrative passwords
Cisco advises that customers who cannot upgrade to a fixed software release should immediately reinstall their current software release from a copy of software from Cisco.com and change any administrative passwords until they can upgrade to a fixed software release.
Customers should follow best practices for the image downloaded from Cisco.com by validating the SHA512 checksum value, available on Cisco.com, prior to installing the downloaded software.
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The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
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Cisco would like to thank Rui Ataide and Hermes Bojaxhi of NetWitness Incident Response Team for reporting this vulnerability.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2021-AUG-18
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