A thunderbird security update has been released for Debian GNU/Linux 10 and 11 to address multiple security issues.

DSA 5034-1: thunderbird security update

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Debian Security Advisory DSA-5034-1 security@debian.org
  https://www.debian.org/security/ Moritz Muehlenhoff
January 02, 2022   https://www.debian.org/security/faq
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Package : thunderbird
CVE ID : CVE-2021-4126 CVE-2021-38496 CVE-2021-38500 CVE-2021-38502
CVE-2021-38503 CVE-2021-38504 CVE-2021-38506 CVE-2021-38507
CVE-2021-38508 CVE-2021-38509 CVE-2021-43528 CVE-2021-43529
CVE-2021-43534 CVE-2021-43535 CVE-2021-43536 CVE-2021-43537
CVE-2021-43538 CVE-2021-43539 CVE-2021-43541 CVE-2021-43542
CVE-2021-43543 CVE-2021-43545 CVE-2021-43546 CVE-2021-44538

Multiple security issues were discovered in Thunderbird, which could
result in the execution of arbitrary code, spoofing, information disclosure,
downgrade attacks on SMTP STARTTLS connections or misleading display of
OpenPGP/MIME signatures.

For the oldstable distribution (buster), these problems have been fixed
in version 1:91.4.1-1~deb10u1.

For the stable distribution (bullseye), these problems have been fixed in
version 1:91.4.1-1~deb11u1.

We recommend that you upgrade your thunderbird packages.

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

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/