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CVE-2026-20307: Cisco Identity Services Engine Software

Severity

9.9 (CRITICAL)

Vendor

CISCO

Affected versions

3.1.0; 3.1.0 p1; 3.1.0 p3

Patch status

Unknown

Published

2026-09-16T17:17:16.973

Modified

2026-09-16T19:16:15.097

Why it matters

Critical vulnerability requiring immediate validation against your environment.

Recommended admin actions

• Prioritize validation immediately due to critical CVSS severity.
• Treat internet-facing systems as higher priority.

Technical summary

A vulnerability in the web-based management interface of Cisco ISE could allow an authenticated, remote attacker to execute arbitrary commands on the underlying operating system of an affected device. To exploit this vulnerability, the attacker must have at least low-privileged administrative credentials. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream. An attacker could exploit this vulnerability by sending a crafted serialized Java object to the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary code on the device and elevate privileges to root. In single-node deployments, successful exploitation of this vulnerability could cause the affected ISE node to become unavailable, resulting in a denial of service (DoS) condition. In that condition, endpoints that have not already authenticated would be unable to access the network until the node is restored.

View the official NVD record for CVE-2026-20307

CVE data is sourced from NVD/CNA records and optional enrichment. Validate against the vendor advisory before taking production action.