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Vulnerability record · CVE-2020-15166 · published 11 September 2020

CVE-2020-15166: Zeromq libzmq uncontrolled resource consumption vulnerability

Zeromq · Libzmq

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.

7.5 CVSS 3.1 High EPSS 3.4% · top 11.6% CWE-400 · Uncontrolled resource consumption
7.5CVSS 3.1 base score, v2 5.0
3.4%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
14References
17 Jun 2026Last modified by NVD

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.

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

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/zeromq/libzmq/pull/3913 PatchThird Party Advisory
https://github.com/zeromq/libzmq/pull/3973 PatchThird Party Advisory
https://github.com/zeromq/libzmq/security/advisories/GHSA-25wp-cf8g-938m PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2020/11/msg00017.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BZ5IMNQXDB52JFBXHFLK4AH
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YFW2ZELCCPS4VLU4OSJOH5Y
https://security.gentoo.org/glsa/202009-12 Third Party Advisory
https://github.com/zeromq/libzmq/pull/3913 PatchThird Party Advisory
https://github.com/zeromq/libzmq/pull/3973 PatchThird Party Advisory
https://github.com/zeromq/libzmq/security/advisories/GHSA-25wp-cf8g-938m PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2020/11/msg00017.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BZ5IMNQXDB52JFBXHFLK4AH
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YFW2ZELCCPS4VLU4OSJOH5Y
https://security.gentoo.org/glsa/202009-12 Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-15166), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.