A libspf2 security update has been released for Debian GNU/Linux 9 LTS to address a denial of service, or potentially execution of arbitrary code when processing a specially crafted SPF record.

DLA 2739-1: libspf2 security update

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Debian LTS Advisory DLA-2739-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Markus Koschany
August 11, 2021   https://wiki.debian.org/LTS
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Package : libspf2
Version : 1.2.10-7+deb9u1
CVE ID : CVE-2021-20314

Philipp Jeitner and Haya Shulman discovered a stack-based buffer
overflow in libspf2, a library for validating mail senders with SPF,
which could result in denial of service, or potentially execution of
arbitrary code when processing a specially crafted SPF record.

For Debian 9 stretch, this problem has been fixed in version
1.2.10-7+deb9u1.

We recommend that you upgrade your libspf2 packages.

For the detailed security status of libspf2 please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/libspf2

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