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Fencer Vulns
high 7.5

CVE-2020-15166 json

Denial of Service in ZeroMQ

published 2020-09-11 6 y ago modified 2026-07-18 3 mo ago also EUVD-2020-7240 , JLSEC-2026-513

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.3%
EPSS 3.3% chance of exploitation in 30 days, percentile 88%
public exploits
0
none known

Summary

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.

Patch / fix

  • julia ZeroMQ_jll 4.3.4+0
  • zeromq libzmq 4.3.3
  • zeromq3 Debian 14, Debian 13, Debian 12 4.3.3-1

debian advisories DEBIAN-CVE-2020-15166

  • zeromq3 Ubuntu Pro 14.04 LTS 4.0.4+dfsg-2ubuntu0.1+esm2
  • zeromq3 Ubuntu Pro 16.04 LTS 4.1.4-7ubuntu0.1+esm1
  • zeromq3 Ubuntu Pro 18.04 LTS 4.2.5-1ubuntu0.2+esm1
  • zeromq3 Ubuntu Pro 20.04 LTS 4.3.2-2ubuntu1.20.04.1~esm1

ubuntu advisories UBUNTU-CVE-2020-15166

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • zeromq SLES for SAP 15, SLES 15-LTSS, SLE Module for Basesystem 15 SP2 +3 more 4.2.3-3.15.4
  • libunwind SLES for SAP 15, SLES 15-LTSS, SLE Module for Package Hub 15 SP2 +5 more 1.2.1-4.2.3

suse advisories SUSE-SU-2020:3264-1

  • zeromq openSUSE Tumbleweed 4.3.4-2.2
  • zeromq openSUSE Leap 15.2 4.2.3-lp152.7.3.1
  • libunwind openSUSE Leap 15.2 1.2.1-lp152.5.3.1
  • zeromq openSUSE Leap 15.1 4.2.3-lp151.5.6.1
  • libunwind openSUSE Leap 15.1 1.2.1-lp151.4.3.1

opensuse advisories openSUSE-SU-2024:11540-1openSUSE-SU-2020:1910-1openSUSE-SU-2020:1907-1

  • zeromq Alpine 3.24, Alpine 3.23, Alpine 3.22 +13 more 4.3.3-r0

alpine advisories ALPINE-CVE-2020-15166

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • zeromq Arch Linux 4.3.3-1

arch linux advisories AVG-1219

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-15166 updated cvss 7.5

zeromq: unauthenticated clients causing denial-of-service

  • Red Hat Ceph Storage 2 zeromq3
    affected: workaround, no fix planned “Out of support scope”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.32% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
julia ZeroMQ_jll
<4.3.4+0
4.3.4+0

Affected products

  • zeromq libzmq

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.