# CVE-2020-27121: Cisco Unified Communications Manager IM and Presence Service Denial of Service Vulnerability

> An authenticated remote attacker can crash the authentication service via crafted login requests, causing a denial of service for new logins.

- **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:** 6 Nov 2020
- **Updated:** 13 Nov 2024
- **Also known as:** GHSA-7c3f-h49g-4mg6

## What is CVE-2020-27121?

CVE-2020-27121 is a medium-severity denial of service vulnerability in Cisco Unified Communications Manager IM and Presence Service, published on 6 Nov 2020. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A vulnerability in Cisco Unified Communications Manager IM & Presence Service (Unified CM IM&P) Software could allow an authenticated, remote attacker to cause the Cisco XCP Authentication Service on an affected device to restart, resulting in a denial of service (DoS) condition. The vulnerability is due to improper handling of login requests. An attacker could exploit this vulnerability by sending a crafted client login request to an affected device. A successful exploit could allow the attacker to cause a process to crash, resulting in a DoS condition for new login attempts. Users who are authenticated at the time of the attack would not be affected. There are workarounds that address this vulnerability.

Weakness: CWE-755 (Improper Handling of Exceptional Conditions), CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2020-27121?

It affects 1 product.


Products: Cisco Unified Communications Manager Im and Presence Service.

## How do I fix CVE-2020-27121?

No fix has been published for CVE-2020-27121 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-27121 being exploited?

There is no known exploitation of CVE-2020-27121 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Unified Communications Manager IM and Presence Service

- [CVE-2018-0363](https://insights.sbomify.com/CVE-2018-0363/): Cross-site request forgery in Cisco Unified Communications Manager IM & Presence Service unknown (high 8.8)
- [CVE-2023-20108](https://insights.sbomify.com/CVE-2023-20108/): Denial of service in Cisco Unified Communications Manager IM and Presence Service (high 7.5)
- [CVE-2016-6464](https://insights.sbomify.com/CVE-2016-6464/): Information disclosure in Cisco Unified Communications Manager (high 7.5)
- [CVE-2016-1466](https://insights.sbomify.com/CVE-2016-1466/): Denial of service in n/a (high 7.5)
- [CVE-2021-1363](https://insights.sbomify.com/CVE-2021-1363/): Cisco Unified Communications Manager IM & Presence Service SQL Injection Vulnerabilities (high 7.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-27121 and fix it if it is affected.

What it is: CVE-2020-27121 is a medium-severity denial of service vulnerability in Cisco Unified Communications Manager IM and Presence Service, published on 6 Nov 2020. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-27121 in the wild and no public exploit code.

Affected product: Cisco Unified Communications Manager IM and Presence Service. 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-2020-27121/ (Markdown: https://insights.sbomify.com/CVE-2020-27121/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-27121
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-27121
- OSV: https://osv.dev/vulnerability/CVE-2020-27121

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-27121/
Summaries are generated and may contain mistakes; the official description above is the record.