An expat regression update has been released for Debian GNU/Linux 10 and 11 to address a regression introduced by the previous update.

DSA 5085-2: expat regression update

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Debian Security Advisory DSA-5085-2 security@debian.org
  https://www.debian.org/security/ Salvatore Bonaccorso
March 13, 2022   https://www.debian.org/security/faq
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Package : expat

The update for expat released as DSA 5085-1 introduced regressions for
applications using URI characters (':' in particular) for a namespace
separator (while the HTML API docs of function XML_ParserCreateNS have
been advising against their use). Updated expat packages are now
available which relax the fix for CVE-2022-25236 with regard to RFC 3986
URI characters.

For the oldstable distribution (buster), this problem has been fixed
in version 2.2.6-2+deb10u4.

For the stable distribution (bullseye), this problem has been fixed in
version 2.2.10-2+deb11u3.

We recommend that you upgrade your expat packages.

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

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/