Cisco Adaptive Security Appliance Software Kerberos Authentication Bypass Vulnerability

A vulnerability in the Kerberos authentication feature of Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to impersonate the Kerberos key distribution center (KDC) and bypass authentication on an affected device that is configured to perform Kerberos authentication for VPN or local device access.

The vulnerability is due to insufficient identity verification of the KDC when a successful authentication response is received. An attacker could exploit this vulnerability by spoofing the KDC server response to the ASA device. This malicious response would not have been authenticated by the KDC. A successful attack could allow an attacker to bypass Kerberos authentication.

Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

Note: Configuration changes after the software upgrade are necessary to address this vulnerability. See the Details [“#details”] section of this advisory for additional information.

This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-asa-kerberos-bypass-96Gghe2sS [“https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-asa-kerberos-bypass-96Gghe2sS”]

This advisory is part of the May 2020 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication, which includes 12 Cisco Security Advisories that describe 12 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: May 2020 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication [“https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-73830”].