A xterm security update has been released for Debian GNU/Linux 9 LTS a denial of service issue.

DLA 2558-1: xterm security update

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Debian LTS Advisory DLA-2558-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Utkarsh Gupta
February 14, 2021   https://wiki.debian.org/LTS
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Package : xterm
Version : 327-2+deb9u1
CVE ID : CVE-2021-27135
Debian Bug : 982439

xterm through Patch #365 allows remote attackers to cause a
denial of service (segmentation fault) or possibly have
unspecified other impact via a crafted UTF-8 character sequence.

For Debian 9 stretch, this problem has been fixed in version
327-2+deb9u1.

We recommend that you upgrade your xterm packages.

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

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