Skip to content
VulniPulse
Sign in
High8.6Cisco Updated

High [CVE-2026-20301] Cisco IOS Software and IOS XE Software Extensible Messaging Client Protocol Denial of Service Vulnerability

This high-severity Cisco advisory covers CVE-2026-20301 affecting IOS XE Software.

cisco-sa-ios-xmcp-thbAr34t Published Aug 5, 2026Updated by vendor Aug 5, 2026
CVE-2026-20301
Affected products & platforms
CiscoIOS XE
Open vendor advisory

Android app · Google Play

Monitor future Cisco CVEs from your phone.

Choose a whole vendor or a precise platform, then receive matching security advisories by phone notification, email, or both. Coverage follows 32 official vendor sources and 160+ reviewed platform categories.

Matching phone alertsOptional email delivery
Get CVE alertsSee app features

Summary

A vulnerability in the Extensible Messaging Client Protocol (XMCP), also referred to as the External Client protocol, of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

This vulnerability is due to improper handling of malformed XMCP packets. An attacker could exploit this vulnerability by sending a malformed XMCP packet to an affected device.

A successful exploit could allow the attacker to cause the affected device to reload unexpectedly, resulting in a DoS condition. The attacker does not need the XMCP client username to exploit this vulnerability.

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

There is a mitigation that addresses this vulnerability.

Affected versions
  • Scope: This vulnerability affects Cisco devices if they are running a vulnerable release of Cisco IOS Software or IOS XE Software and have the XMCP Server feature enabled.

Official advisory · high-confidence parse· fetched 2 hours ago·verify at source

Fixed versions

No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.

Official advisory · high-confidence parse· fetched 2 hours ago·verify at source

Mitigation checklist

Temporary workarounds
  • There are no workarounds that address this vulnerability. However, as a mitigation, administrators may configure an access control allow list to allow only clients that match the specified access list to connect. All other clients will be denied. In the following example configuration, only host 192.168.1.1 is allowed to connect.
  • service-routing xmcp listen
  • allow-list ipv4 XMCPClientListIPv4
  • client username test_xmcp password
  • !
  • ip access-list extended XMCPClientListIPv4
  • permit tcp host 192.168.1.1 any

Official advisory · high-confidence parse· fetched 2 hours ago·verify at source

Discussion(0)

No comments yet. Share field notes, upgrade gotchas, or questions — verify against the vendor advisory before acting on community advice.

Sign in to join the discussion.