A libebml security update has been released for Debian GNU/Linux 9 LTS to address a heap overflow issue.

DLA 2629-1: libebml security update

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Debian LTS Advisory DLA-2629-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Thorsten Alteholz
April 18, 2021   https://wiki.debian.org/LTS
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Package : libebml
Version : 1.3.4-1+deb9u2
CVE ID : CVE-2021-3405

A heap overflow issue was detected in libebml, a library to read and
write files in the EBML format, a binary pendant to XML.
These issues appeared in several ReadData functions of various data type
classes. This update also fixes the issue in EbmlString::ReadData and
EbmlUnicodeString::ReadData, which were mentioned in CVE-2021-3405.

For Debian 9 stretch, this problem has been fixed in version
1.3.4-1+deb9u2.

We recommend that you upgrade your libebml packages.

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

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