Admins who use Cisco Webex Services configured to use trust anchors within the SSO integration with Control Hub must install a new identity provider certificate to close a critical vulnerability, or risk losing access control.

Cisco said in an advisory this week that admins must upload a new identity provider (IdP) SAML certificate to Webex Control Hub, the web-based management portal where IT administrators can control all Cisco Webex services, including certificate management, meetings, messaging and calling. Failure to close this hole will allow an unauthenticated, remote attacker to impersonate any user within the service.

The vulnerability, CVE-2026-20184, carries a CVSS score of 9.8.

Because Webex is a cloud service, Cisco can, and has, patched its side of the application. But admins using single-sign on (SSO) still need to install the new certificate. There are no workarounds.

A Webex support article on managing SSO integration says that information about certificates is found in the Webex Control Hub Alerts center, where customers can view which ones are installed, and their status. The Control Hub also contains an SSO wizard to aid in updating certificates. The article contains step-by-step details on the process.

Asked for comment, and for more details about the vulnerability, a Cisco spokesperson didn’t go beyond the advisory. “Cisco published a security advisory disclosing a vulnerability in the integration of single sign-on with Control Hub in Cisco Webex Services,” the spokesperson said. “At the time of publication (April 15) Cisco had addressed the vulnerability, and was not aware of any malicious use of this vulnerability. Affected customers must update their SAML certificate to ensure uninterrupted services.”

Gartner analyst Peter Firstbrook noted in an email that, since Cisco has applied the patch to the cloud service, this is more of a configuration change. But that doesn’t minimize the possible damage. “While we are not aware of exploits using this vulnerability, users can lose SSO access to Webex without this change,” he said. 

“This does illustrate a bigger trend that identity and access management is the corporate perimeter,” he added, “and the majority of attacks include an identity and access management component. CISOs must increase their focus on IAM hygiene, particularly as agentic computing is accelerating.” 

Identity and access management is, of course, the keystone of cybersecurity. As Crowdstrike observed in its 2026 Global Threat Report, abuse of valid accounts accounted for 35% of cloud incidents it investigated last year, “reinforcing that identity has become central to intrusion.” Single sign-on allows a user to authenticate to multiple applications through one set of credentials. It’s efficient, and, of more importance to a CSO, strengthens security.

Additional critical fixes

The Webex flaw is one of three critical vulnerabilities Cisco identified and issued patches for this week. In addition, multiple vulnerabilities have to be patched in Cisco Identity Services Engine (ISE) and Cisco ISE Passive Identity Connector (ISE-PIC).

These holes (CVE-2026-20147 and CVE-2026-20148, which carry CVSS scores of 9.9), could allow an authenticated, remote attacker to perform remote code execution or conduct path traversal attacks on an affected device. To exploit these vulnerabilities, the attacker must have valid administrative credentials, and send a crafted HTTP request to an affected device. There are no workarounds.

Separately, two more vulnerabilities were found in ISE that could lead to remote code execution on the underlying operating system of an affected device. To exploit these vulnerabilities (CVE-2026-20180 and CVE-2026-20186), the attacker would only need Read Only Admin credentials.