CVE-2021-1592: Cisco UCS Manager Software SSH Sessions Denial of Service Vulnerability

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-08-25 · updated 2026-06-17
Weakness: CWE-664

Description

A vulnerability in the way Cisco UCS Manager software handles SSH sessions could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper resource management for established SSH sessions. An attacker could exploit this vulnerability by opening a significant number of SSH sessions on an affected device. A successful exploit could allow the attacker to cause a crash and restart of internal Cisco UCS Manager software processes and a temporary loss of access to the Cisco UCS Manager CLI and web UI. Note: The attacker must have valid user credentials to authenticate to the affected device.

Affected products

Cisco Unified Computing System (Managed): from 4.0 before 4.0\(4m\); from 4.1 before 4.1\(3e\) — fixed in 4.0\(4m\), 4.1\(3e\)

How to fix

Upgrade to a fixed version: Cisco Unified Computing System (Managed) 4.0\(4m\), 4.1\(3e\). Check the vendor advisory for mitigations.

References

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