A Thunderbird security update has been released for Ubuntu Linux 20.10.

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Ubuntu Security Notice USN-4736-1
February 16, 2021

thunderbird vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.10

Summary:

Several security issues were fixed in Thunderbird.

Software Description:
- thunderbird: Mozilla Open Source mail and newsgroup client

Details:

Multiple security issues were discovered in Thunderbird. If a user were
tricked into 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 arbitrary code. (CVE-2020-26976,
CVE-2021-23953, CVE-2021-23954, CVE-2021-23960, CVE-2021-23964)

It was discovered that responses received during the plaintext phase of
the STARTTLS connection setup were subsequently evaluated during the
encrypted session. A person in the middle could potentially exploit this
to perform a response injection attack. (CVE-2020-15685)

Update instructions:

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

Ubuntu 20.10:
thunderbird 1:78.7.1+build1-0ubuntu0.20.10.4

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

References:
  https://usn.ubuntu.com/4736-1
CVE-2020-15685, CVE-2020-26976, CVE-2021-23953, CVE-2021-23954,
CVE-2021-23960, CVE-2021-23964

Package Information:

  https://launchpad.net/ubuntu/+source/thunderbird/1:78.7.1+build1-0ubuntu0.20.10.4