Status: EXPLOITED | Advisory ID: CVE-2026-20301
| CVE | CVE-2026-20301 |
| CVSS Score / Version | 8.6 (High) / CVSS v3.1 |
| Updated | 2026-09-20 |
| CVSS Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
| CVSS Prose | attack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is changed; confidentiality impact is none; integrity impact is none; availability impact is high. |
| Affected products | Cisco IOS XE and Cisco IOS |
| Exploitation status | The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory. |
| Classified as | CWE-606 (Unchecked Input for Loop Condition) |
| Exploitation prediction (EPSS) | 0.57% probability of exploitation in the next 30 days (45% percentile) -- FIRST.org's EPSS model. |
| Vendor | Product | Affected Versions | Patch Status |
|---|---|---|---|
| Cisco | IOS XE | ||
| Cisco | IOS |
| Subsystems | Industrial Network - Routers/Firewalls |
| Sectors | Critical Manufacturing, Energy, Transportation Systems, Water and Wastewater Systems |
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.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. There is a mitigation that addresses this vulnerability.