CVE-2021-1594: A vulnerability in the REST API of Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to perform a command injection...

Description

A vulnerability in the REST API of Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to perform a command injection attack and elevate privileges to root. This vulnerability is due to insufficient input validation for specific API endpoints. An attacker in a man-in-the-middle position could exploit this vulnerability by intercepting and modifying specific internode communications from one ISE persona to another ISE persona. A successful exploit could allow the attacker to run arbitrary commands with root privileges on the underlying operating system. To exploit this vulnerability, the attacker would need to decrypt HTTPS traffic between two ISE personas that are located on separate nodes.

Metrics

CVSS 3.1

8.1/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.40%

69.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Cisco	Identity Services Engine	>= 2.4.0, < 2.6.0
Cisco	Identity Services Engine	2.4\(0.902\)
Cisco	Identity Services Engine	2.6\(0.156\)
Cisco	Identity Services Engine	2.6.0
Cisco	Identity Services Engine	2.7\(0.903\)
Cisco	Identity Services Engine	2.7.0
Cisco	Identity Services Engine	3.0\(0.458\)
Cisco	Identity Services Engine	3.0.0
Cisco	Identity Services Engine	3.1\(0.440\)

References

Timeline

Published: Oct 6, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-1594?

A vulnerability in the REST API of Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to perform a command injection attack and elevate privileges to root. This vulnerability is due to insufficient input validation for specific API endpoints. An attacker in a man-in-the-middle position could exploit this vulnerability by intercepting and modifying specific internode communications from one ISE persona to another ISE persona. A successful exploit could allow the attacker to run arbitrary commands with root privileges on the underlying operating system. To exploit this vulnerability, the attacker would need to decrypt HTTPS traffic between two ISE personas that are located on separate nodes.

How severe is CVE-2021-1594?

CVE-2021-1594 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 1.40% probability of exploitation in the next 30 days.

How do I fix CVE-2021-1594?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.