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

> Authenticated attackers can cause a denial of service by opening excessive SSH sessions, crashing Cisco UCS Manager processes.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Aug 2021
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-g536-3jmm-mp33

## What is CVE-2021-1592?

CVE-2021-1592 is a medium-severity denial of service vulnerability in Cisco Unified Computing System, published on 25 Aug 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-664 (Improper Control of a Resource Through its Lifetime)

## Which versions are affected by CVE-2021-1592?

It affects 1 product.


Products: Cisco Unified Computing System.

## How do I fix CVE-2021-1592?

No fix has been published for CVE-2021-1592 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-1592 being exploited?

There is no known exploitation of CVE-2021-1592 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Unified Computing System

- [CVE-2026-20200](https://insights.sbomify.com/CVE-2026-20200/): Cisco Integrated Management Controller Argument Injection and Remote Code Execution Vulnerability (high 8.8)
- [CVE-2026-20094](https://insights.sbomify.com/CVE-2026-20094/): Cisco Integrated Management Controller Command Injection Vulnerability (high 8.8)
- [CVE-2018-0430](https://insights.sbomify.com/CVE-2018-0430/): Cisco Integrated Management Controller Command Injection Vulnerability (high 8.8)
- [CVE-2018-0431](https://insights.sbomify.com/CVE-2018-0431/): Cisco Integrated Management Controller Command Injection Vulnerability (high 8.8)
- [CVE-2012-4078](https://insights.sbomify.com/CVE-2012-4078/): Auth bypass in n/a (high 8.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-1592 and fix it if it is affected.

What it is: CVE-2021-1592 is a medium-severity denial of service vulnerability in Cisco Unified Computing System, published on 25 Aug 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-1592 in the wild and no public exploit code.

Affected product: Cisco Unified Computing System. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-1592/ (Markdown: https://insights.sbomify.com/CVE-2021-1592/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1592
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1592
- OSV: https://osv.dev/vulnerability/CVE-2021-1592

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-1592/
Summaries are generated and may contain mistakes; the official description above is the record.