An icu security update has been for Debian GNU/Linux 10.

DSA 5014-1: icu security update

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Debian Security Advisory DSA-5014-1 security@debian.org
  https://www.debian.org/security/ Salvatore Bonaccorso
November 28, 2021   https://www.debian.org/security/faq
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Package : icu
CVE ID : CVE-2020-21913

Rongxin Wu discovered a use-after-free vulnerability in the
International Components for Unicode (ICU) library which could result in
denial of service or potentially the execution of arbitrary code.

For the oldstable distribution (buster), this problem has been fixed
in version 63.1-6+deb10u2.

We recommend that you upgrade your icu packages.

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

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://www.debian.org/security/