Debian LTS: DLA-3783-1 Moderate Expat Denial of Service Vulnerability

When parsing a really big token that requires multiple buffer fills to
complete, expat has to re-parse the token from start multiple times,
which takes time. These patches introduce a heuristic that, when having
failed on the same token multiple times, defers further parsing until
there's significantly more data available.

The patch also introduces an optiional API,
XML_SetReparseDeferralEnabled(), to disable the new heuristic.

For Debian 10 buster, this problem has been fixed in version
2.2.6-2+deb10u7.

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/source-package/expat

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