USN-4421-1: Thunderbird vulnerabilities

08 July 2020

Several security issues were fixed in Thunderbird.



  • thunderbird - Mozilla Open Source mail and newsgroup client


Multiple security issues were discovered in Thunderbird. If a user were
tricked in to opening a specially crafted website in a browsing context,
an attacker could potentially exploit these to cause a denial of service,
obtain sensitive information, or execute arbtirary code. (CVE-2020-12405,
CVE-2020-12406, CVE-2020-12410, CVE-2020-12417, CVE-2020-12418,
CVE-2020-12419, CVE-2020-12420)

It was discovered that Thunderbird would continue an unencrypted
connection when configured to use STARTTLS for IMAP if the server
responded with PREAUTH. A remote attacker could potentially exploit
this to perform a person-in-the-middle attack in order to obtain
sensitive information. (CVE-2020-12398)

It was discovered that NSS showed timing differences when performing DSA
signatures. An attacker could potentially exploit this to obtain private
keys using a timing attack. (CVE-2020-12399)

It was discovered that when performing add-on updates, certificate chains
not terminating with built-in roots were silently rejected. This could
result in add-ons becoming outdated. (CVE-2020-12421)

Update instructions

The problem can be corrected by updating your system to the following package versions:

Ubuntu 20.04
Ubuntu 19.10
Ubuntu 18.04
Ubuntu 16.04

After a standard system update you need to restart Thunderbird to make
all the necessary changes.