A netty security update has been released for Debian GNU/Linux 9 LTS to address an insecure temporary file issue.

DLA 2555-1: netty security update

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Debian LTS Advisory DLA-2555-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Chris Lamb
February 11, 2021   https://wiki.debian.org/LTS
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Package : netty
Version : 1:4.1.7-2+deb9u3
CVE ID : CVE-2021-21290

It was discovered that there was an insecure temporary file issue
that could have lead to disclosure of arbitrary local files.

For Debian 9 "Stretch", this problem has been fixed in version
1:4.1.7-2+deb9u3.

We recommend that you upgrade your netty packages.

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

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