Identity Services Engine
CVE-2025-20343: Cisco Identity Services Engine Radius Suppression Denial of Service Vulnerability
A vulnerability in the RADIUS setting Reject RADIUS requests from clients with repeated failures on Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to cause Cisco ISE to restart unexpectedly.
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Cisco Identity Services Engine Software 3.4 | See the advisory |
| Cisco Identity Services Engine Software 3.4 Patch 1 | See the advisory |
| Cisco Identity Services Engine Software 3.4 Patch 2 | See the advisory |
| Cisco Identity Services Engine Software 3.4 Patch 3 | See the advisory |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
A vulnerability in the RADIUS setting Reject RADIUS requests from clients with repeated failures on Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to cause Cisco ISE to restart unexpectedly.
This vulnerability is due to a logic error when processing a RADIUS access request for a MAC address that is already a rejected endpoint. An attacker could exploit this vulnerability by sending a specific sequence of multiple crafted RADIUS access request messages to Cisco ISE. A successful exploit could allow the attacker to cause a denial of service (DoS) condition when Cisco ISE restarts.
Exploitation
The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 11 Oct 2026.