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Vulnerability record · CVE-2026-20301 · published 5 August 2026

CVE-2026-20301: Cisco ios vulnerability

Cisco · Ios

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.

8.6 CVSS 3.1 High EPSS 0.57% · top 54.8% CWE-606 · CWE-606
8.6CVSS 3.1 base score
0.57%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
1References
17 Sep 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-xmcp-thbAr34t MitigationVendor Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-20301), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.