Cisco Identity Services Engine up to 3.5.0 deserialization

Summaryinfo

A vulnerability was found in Cisco Identity Services Engine. It has been classified as very critical. Impacted is an unknown function. The manipulation leads to deserialization. This vulnerability is listed as CVE-2026-20211. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Cisco Identity Services Engine and classified as very critical. This issue affects an unknown code block. The manipulation with an unknown input leads to a deserialization vulnerability. Using CWE to declare the problem leads to CWE-502. The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at sec.cloudapps.cisco.com. The identification of this vulnerability is CVE-2026-20211 since 10/08/2025. The exploitation is known to be easy. The attack may be initiated remotely. Additional levels of successful authentication are necessary for exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/16/2026).

Upgrading eliminates this vulnerability.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Policy Management Software

Vendor

• Cisco

Name

• Identity Services Engine

Version

• 3.1.0
• 3.1.0 p1
• 3.1.0 p2
• 3.1.0 p3
• 3.1.0 p4
• 3.1.0 p5
• 3.1.0 p6
• 3.1.0 p7
• 3.1.0 p8
• 3.1.0 p9
• 3.1.0 p10
• 3.1.0 p11
• 3.1.0 p72
• 3.2.0
• 3.2.0 p1
• 3.2.0 p2
• 3.2.0 p3
• 3.2.0 p4
• 3.2.0 p5
• 3.2.0 p6
• 3.2.0 p7
• 3.3.0
• 3.4.0
• 3.5.0

License

• commercial

Website

• Vendor: https://www.cisco.com/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Be aware that VulDB is the high quality source for vulnerability data.

Discussion