Cisco IOS XE Software for Catalyst 9800 Series Wireless Controller for Cloud Unauthenticated Access to Certificate Enrollment Service Vulnerability

TL;DR 📌

A medium-severity vulnerability has been identified in the Cisco IOS XE Software for Catalyst 9800 Series Wireless Controllers for Cloud. This flaw allows unauthenticated remote attackers to access the public-key infrastructure (PKI) server, potentially enabling unauthorized device enrollment. Workarounds are available, and Cisco has recommended software updates to fully mitigate the risk.

What happened 🕵️‍♂️

A vulnerability in the Day One setup process of Cisco IOS XE Software for Catalyst 9800 Series Wireless Controllers for Cloud could allow an unauthenticated, remote attacker to access the PKI server running on affected devices. This issue arises due to incomplete cleanup after the Day One setup process. An attacker could exploit this vulnerability by sending Simple Certificate Enrollment Protocol (SCEP) requests, potentially allowing them to request a certificate and join an attacker-controlled device to the virtual wireless controller.

Affected products 🖥️

The vulnerability affects Cisco IOS XE Software for Catalyst 9800 Series Wireless Controllers for Cloud, regardless of device configuration. Cisco has confirmed that this vulnerability does not affect Cisco IOS XE Software for Catalyst 9800 Series Wireless Hardware-based Controllers.

Fixed software 🔧

Upgrade to the first fixed release in your train (or later):

Workarounds 🧯

Administrators can mitigate the vulnerability by shutting down the PKI server that matches the hostname of the wireless LAN controller (WLC). The following commands can be used:

vewlc# conf t
vewlc(config)# crypto pki server vewlc_WLC_CA
vewlc(cs-server)# shutdown
vewlc(cs-server)# exit
vewlc# write memory

While this workaround has been tested successfully, customers should evaluate its applicability and potential impact on their specific environments before implementation.

Risk in context 🎯

The highest CVSS score for this vulnerability is 5.3, categorizing it as Medium severity. The risk is primarily due to the potential for unauthorized access and device enrollment, which could lead to further exploitation within the network. While there is no immediate public exploitation reported, the vulnerability’s nature poses a significant risk if left unaddressed.

Fast facts ⚡

• Vulnerability: Unauthenticated access to PKI server
• CVSS Score: 5.3 (Medium)
• Exploitation Potential: Requires no authentication
• Workarounds Available: Yes
• Public Exploitation: None reported

For leadership 🧭

Executive summary. Cloud-based Catalyst 9800 wireless controllers can be reached by unauthenticated attackers who submit certificate requests to the built-in PKI server, potentially adding a device they control to the wireless network. There is no evidence of active exploitation, so this can go through normal patch and change processes rather than emergency response.

Why it matters:

• The flaw sits in the SCEP-based certificate enrollment service left exposed after the Day One setup process on Catalyst 9800 Series Wireless Controllers for Cloud - hardware-based 9800 controllers are not affected.
• No authentication is needed: an attacker who can reach the PKI server can send SCEP requests and obtain a certificate, which can be used to join an attacker-controlled device to the virtual WLC.
• A rogue device joining the controller could gain a foothold inside the wireless infrastructure, giving an attacker a platform for further action against the network.
• The exposure exists regardless of how the device is otherwise configured, so configuration hardening elsewhere will not close this particular gap.

Now / Next / Later:

• Now: Identify all Cisco IOS XE Catalyst 9800 Series Wireless Controller for Cloud instances and check whether their PKI server (matching the WLC hostname) is still running and reachable.
• Next: Apply the documented workaround - shut down the matching crypto pki server (e.g. vewlc_WLC_CA) via configuration and save with write memory - on any instance that cannot be immediately patched.
• Later: Schedule an upgrade to a fixed IOS XE release for the affected cloud controllers and review Day One provisioning procedures to ensure PKI enrollment services are properly torn down or restricted after setup completes.