[xml/sgml-pkgs] Bug#988603: libxml2: CVE-2021-3541: Exponential entity expansion attack bypasses all existing protection mechanisms

[Salvatore Bonaccorso]

Source: libxml2
Version: 2.9.10+dfsg-6.6
Severity: important
Tags: security upstream
Forwarded: https://gitlab.gnome.org/GNOME/libxml2/-/issues/228
X-Debbugs-Cc: carnil at debian.org, Debian Security Team <team at security.debian.org>

Hi,

The following vulnerability was published for libxml2.

CVE-2021-3541[0]:
| Exponential entity expansion attack bypasses all existing protection
| mechanisms

Technical details for the vulnerability are unfortunately not public,
but it looks that the flaw is essentially a variant of the billion
laughts attack (CVE-2003-1564) which can lead to denial of service for
applications using libxml2.

If you fix the vulnerability please also make sure to include the
CVE (Common Vulnerabilities & Exposures) id in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2021-3541
    https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-3541
[1] https://gitlab.gnome.org/GNOME/libxml2/-/issues/228
[2] https://gitlab.gnome.org/GNOME/libxml2/-/commit/8598060bacada41a0eb09d95c97744ff4e428f8e

Please adjust the affected versions in the BTS as needed.

Regards,
Salvatore