A GNU Screen security update has been released for Ubuntu Linux 16.04 LTS, 18.04 LTS, 20.04 LTS, and 20.10.

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Ubuntu Security Notice USN-4747-1
February 24, 2021

screen vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

GNU Screen could be made to crash or run programs if it processed specially
crafted character sequences.

Software Description:
- screen: terminal multiplexer with VT100/ANSI terminal emulation

Details:

Felix Weinmann discovered that GNU Screen incorrectly handled certain
character sequences. A remote attacker could use this issue to cause GNU
Screen to crash, resulting in a denial of service, or possibly execute
arbitrary code.

Update instructions:

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

Ubuntu 20.10:
screen 4.8.0-2ubuntu0.1

Ubuntu 20.04 LTS:
screen 4.8.0-1ubuntu0.1

Ubuntu 18.04 LTS:
screen 4.6.2-1ubuntu1.1

Ubuntu 16.04 LTS:
screen 4.3.1-2ubuntu0.1

In general, a standard system update will make all the necessary changes.

References:
  https://usn.ubuntu.com/4747-1
CVE-2021-26937

Package Information:
  https://launchpad.net/ubuntu/+source/screen/4.8.0-2ubuntu0.1
  https://launchpad.net/ubuntu/+source/screen/4.8.0-1ubuntu0.1
  https://launchpad.net/ubuntu/+source/screen/4.6.2-1ubuntu1.1
  https://launchpad.net/ubuntu/+source/screen/4.3.1-2ubuntu0.1