A zeromq3 security update has been released for Debian GNU/Linux 9 LTS to address a denial of service issue affecting authenticated and encrypted clients.

DLA 2443-1: zeromq3 security update

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Debian LTS Advisory DLA-2443-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Utkarsh Gupta
November 10, 2020   https://wiki.debian.org/LTS
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Package : zeromq3
Version : 4.2.1-4+deb9u3
CVE ID : CVE-2020-15166

It was discovered that ZeroMQ, a lightweight messaging kernel
library does not properly handle connecting peers before a
handshake is completed. A remote, unauthenticated client connecting
to an application using the libzmq library, running with a socket
listening with CURVE encryption/authentication enabled can take
advantage of this flaw to cause a denial of service affecting
authenticated and encrypted clients.

For Debian 9 stretch, this problem has been fixed in version
4.2.1-4+deb9u3.

We recommend that you upgrade your zeromq3 packages.

For the detailed security status of zeromq3 please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/zeromq3

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://wiki.debian.org/LTS