---
title: "CVE-2020-15166\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2020-15166?format=md
keywords: index, follow
---

# CVE-2020-15166

Publication date 11 September 2020

Last updated 18 August 2025

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**7.5 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2020-15166?format=md#impact-score)

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## Description

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability.
Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are
impacted. If a raw TCP socket is opened and connected to an endpoint that
is fully configured with CURVE/ZAP, legitimate clients will not be able to
exchange any message. Handshakes complete successfully, and messages are
delivered to the library, but the server application never receives them.
This is patched in version 4.3.3.

### From the Ubuntu Security Team

It was discovered that ZeroMQ mishandled certain network traffic. An
unauthenticated attacker could use this vulnerability to cause a
denial-of-service and prevent legitimate clients from communicating with
ZeroMQ.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| zeromq3 | 26.04 LTS resolute | Not affected |
| 25.10 questing | Not affected |
| 25.04 plucky | Not affected |
| 24.10 oracular | Not affected |
| 24.04 LTS noble | Not affected |
| 23.10 mantic | Not affected |
| 23.04 lunar | Not affected |
| 22.10 kinetic | Not affected |
| 22.04 LTS jammy | Not affected |
| 21.10 impish | Not affected |
| 21.04 hirsute | Not affected |
| 20.10 groovy | Ignored end of life |
| 20.04 LTS focal | Fixed 4.3.2-2ubuntu1.20.04.1~esm1  Ubuntu Pro |
| 18.04 LTS bionic | Fixed 4.2.5-1ubuntu0.2+esm1  Ubuntu Pro |
| 16.04 LTS xenial | Fixed 4.1.4-7ubuntu0.1+esm1  Ubuntu Pro |
| 14.04 LTS trusty | Fixed 4.0.4+dfsg-2ubuntu0.1+esm2  Ubuntu Pro |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

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## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

7.5 · High

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Privileges required | None |
  | User interaction | None |
  | Scope | Unchanged |
  | Confidentiality impact | None |
  | Integrity impact | None |
  | Availability impact | High |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 7.5 · High |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15166)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2020-15166)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2020-15166)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2020-15166)

### Related Ubuntu Security Notices (USN)

+ [USN-4920-1](https://usn.ubuntu.com/USN-4920-1)
+ ZeroMQ vulnerabilities
+ 15 June 2022

### Other references

* <https://www.openwall.com/lists/oss-security/2020/09/07/3>
* <https://github.com/zeromq/libzmq/security/advisories/GHSA-25wp-cf8g-938m>
* <https://github.com/zeromq/libzmq/commit/e7f0090b161ce6344f6bd35009816a925c070b09>
* <https://www.cve.org/CVERecord?id=CVE-2020-15166>