CVE-2026-20301

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 v3 8.6 HIGH

8.6^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 4.0

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope CHANGED

References

Link	Resource
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-xmcp-thbAr34t

Configurations

No configuration.

History

No history.

Information

Published : 2026-08-05 17:16

Updated : 2026-08-06 15:44

NVD link : CVE-2026-20301

Mitre link : CVE-2026-20301

CVE.ORG link : CVE-2026-20301

JSON object : View

Products Affected

No product.

CWE

CWE-606

Unchecked Input for Loop Condition

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"15.9(3)M3b"}, {"status": "affected", "version": "15.6(2)SP7"}, {"status": "affected", "version": "15.6(2)SP5"}, {"status": "affected", "version": "15.6(2)SP8"}, {"status": "affected", "version": "15.6(2)SP6"}, {"status": "affected", "version": "15.6(2)SP4"}, {"status": "affected", "version": "15.6(2)SP9"}, {"status": "affected", "version": "15.6(2)SP8a"}, {"status": "affected", "version": "15.9(3)M9a"}, {"status": "affected", "version": "15.2(8)E6"}, {"status": "affected", "version": "15.9(3)M10"}, {"status": "affected", "version": "15.2(7)E11"}, {"status": "affected", "version": "15.5(1)SY14"}, {"status": "affected", "version": "15.2(8)E7"}, {"status": "affected", "version": "15.2(4)E10e"}, {"status": "affected", "version": "15.9(3)M11"}, {"status": "affected", "version": "15.2(7)E12"}, {"status": "affected", "version": "15.5(1)SY15"}, {"status": "affected", "version": "15.2(8)E8"}, {"status": "affected", "version": "15.5(1)SY16"}, {"status": "affected", "version": "15.2(7)E13"}, {"status": "affected", "version": "15.9(3)M12"}, {"status": "affected", "version": "15.5(1)SY17"}, {"status": "affected", "version": "15.2(7)E14"}, {"status": "affected", "version": "15.9(3)M13"}], "defaultStatus": "unknown"}]}], "published": "2026-08-05T17:16:50.187", "references": [{"url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-xmcp-thbAr34t", "source": "psirt@cisco.com"}], "vulnStatus": "Awaiting Analysis", "weaknesses": [{"type": "Secondary", "source": "psirt@cisco.com", "description": [{"lang": "en", "value": "CWE-606"}]}], "descriptions": [{"lang": "en", "value": "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.\r\n\r\nThis 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."}], "lastModified": "2026-08-06T15:44:56.043", "sourceIdentifier": "psirt@cisco.com"}