Vulnerability in Cisco iOS Xe Software
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.
EPSS: 0.003 (26.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.
Affected products
- Cisco Ios Xe Software — versions 17.2.1a, 16.12.1y, 16.12.3s
- Cisco Ios — versions 15.9(3)m13, 15.2(8)e4, 15.2(7)e0s
- Cisco Ios_xe — versions 16.10.1, 16.10.1a, 16.10.1b
Weakness classification (CWE)
References
- psirt@cisco.com (Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-20301?
- CVE-2026-20301 is a high-severity vulnerability in Cisco iOS Xe Software, classified under CWE-606. CVSS score: 8.6/10. Published 2026-08-05.
- How severe is CVE-2026-20301?
- High severity. CVSS v3 base score is 8.6 out of 10.