High 8.6Published Aug 5, 2026

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

Updated under an hour ago (Oct 27, 2026, 11:20 PM ET)

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It affects Cisco IOS XE Software and 2 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Cisco IOS XE Software

Exploited in the last 30 days

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: 8.6 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Weakness (CWE): CWE-606
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: cisco
NVD analysis: Analyzed
Record last updated: Aug 5, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Cisco Cisco IOS XE Software cisco:ios_xe_software (from the name)	17.2.1a; 16.12.1y; 16.12.3s; 16.7.1b; 16.6.2; 16.6.5; 16.12.1w; 16.9.1d; and 193 more ranges	CNA record
Cisco IOS cisco:ios (from the name)	15.2(7)E7; 15.2(8)E3; 15.7(3)M10; 15.8(3)M9; 15.9(3)M7; 15.2(7)E8; 15.2(8)E4; 15.9(3)M7a; and 132 more ranges	CNA record
cisco ios cisco:ios	15.2(1)sy6; 15.2(1)sy7; 15.2(1)sy8; 15.2(2)e8; 15.2(2)e9; 15.2(2)e9a; 15.2(2)e10; 15.2(2)e10a; and 132 more ranges	NVD
cisco ios_xe cisco:ios_xe	3.8.10ce; 3.8.10de; 3.11.3ae; 3.11.3e; 3.11.4e; 3.11.5e; 3.11.6e; 3.11.7e; and 193 more ranges	NVD

References

References

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-xmcp-thbAr34t	mitigation, vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.