Vulnerability · Published Aug 5, 2026 · Assigned by cisco
CVE-2026-20301Cisco IOS Software and IOS XE Software Extensible Messaging Client Protocol Denial of Service Vulnerability
High 8.6
In plain English
A high-severity security flaw in Cisco IOS XE Software from Cisco. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 48% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Cisco | Cisco IOS XE Software | 17.2.1a16.12.1y16.12.3s16.7.1b16.6.216.6.516.12.1w16.9.1d |
| Cisco | IOS | 15.2(7)E715.2(8)E315.7(3)M1015.8(3)M915.9(3)M715.2(7)E815.2(8)E415.9(3)M7a |
Weakness: CWE-606 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H