A busybox security update has been released for Debian GNU/Linux 9 LTS to address an issue that causes an invalid free or segmentation fault.

DLA 2614-1: busybox security update

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Debian LTS Advisory DLA-2614-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Markus Koschany
April 01, 2021   https://wiki.debian.org/LTS
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Package : busybox
Version : 1:1.22.0-19+deb9u2
CVE ID : CVE-2021-28831
Debian Bug : 986217

The gunzip decompressor of Busybox, tiny utilities for small and embedded
systems, mishandled the error bit on the huft_build result pointer, with a
resultant invalid free or segmentation fault, via malformed gzip data.

For Debian 9 stretch, this problem has been fixed in version
1:1.22.0-19+deb9u2.

We recommend that you upgrade your busybox packages.

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

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