A ldns security update has been released for Debian GNU/Linux 9 LTS to address four issues.

DLA 2910-1: ldns security update

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Debian LTS Advisory DLA-2910-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Chris Lamb
February 03, 2022   https://wiki.debian.org/LTS
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Package : ldns
Version : 1.7.0-1+deb9u1
CVE IDs : CVE-2020-19860, CVE-2020-19861,
CVE-2017-1000231, CVE-2017-1000232
Debian Bugs : #882014, #882015

It was discovered that there were four issues in ldns, a library used
in Domain Name System (DNS) related programs:

* CVE-2020-19860: When ldns verified a zone file, the
ldns_rr_new_frm_str_internal function had a heap out of bounds
read vulnerability. An attacker could have potentially leaked
information on the heap by constructing a zone file payload.

* CVE-2020-19861: When a zone file in ldns was parsed, the function
ldns_nsec3_salt_data was too trusting of the length value
obtained from the zone file. This could have caused heap overflow
information leakage.

* CVE-2017-1000231: A double-free vulnerability in parse.c could
have resulted in an attack vector. (#882015)

* CVE-2017-1000232: A double-free vulnerability within str2host.c
could have resulted in an attack vector. (#882014)

For Debian 9 "Stretch", these problems have been fixed in version
1.7.0-1+deb9u1.

We recommend that you upgrade your ldns packages.

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

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