A GnuPG security update has been released for Ubuntu Linux 18.04 LTS.

USN-4516-1: GnuPG vulnerability

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Ubuntu Security Notice USN-4516-1
September 17, 2020

gnupg2 vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS

Summary:

GnuPG could be made to expose sensitive information.

Software Description:
- gnupg2: GNU privacy guard - a free PGP replacement

Details:

It was discovered that GnuPG signatures could be forged when the SHA-1
algorithm is being used. This update removes validating signatures based on
SHA-1 that were generated after 2019-01-19. In environments where this is
still required, a new option --allow-weak-key-signatures can be used to
revert this behaviour.

Update instructions:

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

Ubuntu 18.04 LTS:
gnupg 2.2.4-1ubuntu1.3

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

References:
  https://usn.ubuntu.com/4516-1
CVE-2019-14855

Package Information:
  https://launchpad.net/ubuntu/+source/gnupg2/2.2.4-1ubuntu1.3