CVE-2026-20301 json
Cisco IOS Software and IOS XE Software Extensible Messaging Client Protocol Denial of Service Vulnerability
published 2026-08-05 3 mo ago modified 2026-09-17 52 d ago also EUVD-2026-53467
- cvss
- 8.6
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.6%
- EPSS 0.6% chance of exploitation in 30 days, percentile 47%
- public exploits
- 0
- none known
Summary
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.
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 3 mo ago
Exploit prediction
0.57% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 8.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
Affected products
- Cisco Cisco IOS XE Software
- Cisco IOS
Classification
- Weakness
-
- CWE-606 Unchecked Input for Loop Condition
- Technology feeds
References
-
sec.cloudapps.cisco.com
/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-xmcp-thbAr34t
mitigation, vendor-advisory
Sources
- CVE List CVE-2026-20301
- NVD CVE-2026-20301
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