A qt4-x11 security update has been released for Debian GNU/Linux 9 LTS to address multiple out-of-bounds errors.

DLA 2895-1: qt4-x11 security update

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Debian LTS Advisory DLA-2895-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Utkarsh Gupta
January 24, 2022   https://wiki.debian.org/LTS
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Package : qt4-x11
Version : 4:4.8.7+dfsg-11+deb9u3
CVE ID : CVE-2021-3481 CVE-2021-45930
Debian Bug : 986798 1002991

Multiple out-of-bounds error were discovered in qt4-x11.
The highest threat from CVE-2021-3481 (at least) is to data
confidentiality the application availability.

For Debian 9 stretch, these problems have been fixed in version
4:4.8.7+dfsg-11+deb9u3.

We recommend that you upgrade your qt4-x11 packages.

For the detailed security status of qt4-x11 please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/qt4-x11

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