A vulnerability in the meeting-join functionality of Cisco Webex Meetings could have allowed an unauthenticated, network-proximate attacker to complete a meeting-join process in place of an intended targeted user, provided the requisite conditions were satisfied. Cisco has addressed this vulnerability in the Cisco Webex Meetings service, and no customer action is needed. This vulnerability existed due to client certificate validation issues. Prior to this vulnerability being addressed, an attacker could have exploited this vulnerability by monitoring local wireless or adjacent networks for client-join requests and attempting to interrupt and complete the meeting-join flow as another user who was currently joining a meeting. To successfully exploit the vulnerability, an attacker would need the capability to position themselves in a local wireless or adjacent network, to monitor and intercept the targeted network traffic flows, and to satisfy timing requirements in order to interrupt the meeting-join flow and exploit the vulnerability. A successful exploit could have allowed the attacker to join the meeting as another user. However, the Cisco Product Security Incident Response Team (PSIRT) is not aware of any malicious use of the vulnerability that is described in this advisory.