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

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.

Published: 2021-08-25 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-1592 is rated Low Risk (37.6/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.41%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-1592

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-03-30 0.58% 0.41% -0.17%
2 2025-03-29 0.41% 0.58% +0.17%
3 2025-03-17 — 0.41% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-1592

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.8 1.4 [email protected]
4.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.8 1.4 [email protected]
4.0 2.0 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 2.9 [email protected]

Weakness enumeration for CVE-2021-1592

Affected software / configurations for CVE-2021-1592

Vendor Product Version Raw CPE
cisco unified_computing_system >= 4.0, < 4.0\(4m\) cpe:2.3:a:cisco:unified_computing_system:*:*:*:*:*:*:*:*
cisco unified_computing_system >= 4.1, < 4.1\(3e\) cpe:2.3:a:cisco:unified_computing_system:*:*:*:*:*:*:*:*

References for CVE-2021-1592

cvelogic Threat Intelligence