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CVE-2026-20211: Deserialization of Untrusted Data in Cisco Cisco Identity Services Engine Software

0
Critical
VulnerabilityCVE-2026-20211cvecve-2026-20211
Published: 09/16/2026 (09/16/2026, 20:04:10 UTC)
Source: CVE Database V5
Vendor/Project: Cisco
Product: Cisco Identity Services Engine Software

Description

A vulnerability in 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 valid high-privileged administrative credentials. This vulnerability is due to insecure deserialization of Java objects by the affected software. An attacker could exploit this vulnerability by sending a crafted serialized Java object to an affected device. A successful exploit could allow the attacker to obtain user-level access to the underlying operating system and then 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 DoS condition. In that condition, endpoints that have not already authenticated would be unable to access the network until the node is restored.

CVSS v3.1

Score 9.1critical

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Affected software

Cisco

Cisco Identity Services Engine Software

Affected versions
=3.1.0=3.2.0=3.3.0=3.4.0=3.5.0
GitHub Actionsmore threats →ai
cisco/identity-services-engine
pkg:github/cisco/identity-services-engine
Affected versions
=3.1.0=3.2.0=3.3.0=3.4.0=3.5.0

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AI-Powered Analysis

Machine-generated threat intelligence

AILast updated: 09/16/2026, 20:33:21 UTC

Technical Analysis

This vulnerability arises from insecure deserialization of Java objects in Cisco ISE software. An attacker with valid high-privileged administrative credentials can send a crafted serialized Java object to the affected device, resulting in arbitrary command execution on the underlying OS. Successful exploitation can grant user-level access initially, followed by privilege escalation to root. In single-node deployments, exploitation may cause a denial of service by rendering the ISE node unavailable, preventing network access for endpoints that have not authenticated.

Potential Impact

An attacker with high-privileged administrative credentials can execute arbitrary commands on the underlying operating system, potentially gaining root privileges. This can lead to full system compromise. Additionally, in single-node deployments, exploitation can cause a denial of service condition, making the ISE node unavailable and blocking network access for unauthenticated endpoints.

Mitigation Recommendations

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since this vulnerability requires high-privileged administrative credentials, ensure strict access controls and credential management. Monitor Cisco's official advisories for patches or updates addressing this vulnerability.

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Technical Details

Data Version
5.2
Assigner Short Name
cisco
Date Reserved
2025-10-08T11:59:15.398Z
Cvss Version
3.1
State
PUBLISHED

Threat ID: 6aaaf94155bf5e2cf51b934e

Added to database: 09/16/2026, 20:17:05 UTC

Last enriched: 09/16/2026, 20:33:21 UTC

Last updated: 09/17/2026, 05:01:23 UTC

Views: 5

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