CVE-2026-20301

HighCVSS 8.6

Published: 05/08/2026(UTC)Updated: 06/08/2026(UTC)Translated: 05/08/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.33%

25th percentile - higher than 25% of all known CVEs

Summary

A vulnerability in the XMCP protocol of Cisco IOS and IOS XE Software allows an unauthenticated remote attacker to cause a denial of service (DoS) by sending a malformed XMCP packet. The attacker does not need the XMCP client username to exploit this vulnerability.

Risk Assessment

The attack can cause an unexpected device reload, leading to network disruptions and service unavailability.

Recommendation

Apply Cisco IOS and IOS XE software updates that address this vulnerability, and restrict access to the XMCP protocol from trusted sources.

Other vulnerabilities in Cisco IOS and IOS XE Software

CVE-2016-6474High
A vulnerability in the implementation of X.509 Version 3 for SSH authentication functionality in Cisco IOS and IOS XE Software could allow an unauthenticated, remote attacker to bypass authentication on an affected system.

Original NVD description (English source)

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.