CVE-2026-20301Cisco IOS Software and IOS XE Software Extensible Messaging Client Protocol Denial of Service Vulnerability
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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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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
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
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-xmcp-thbAr34tmitigation, 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.