A Libgcrypt security update has been released for Ubuntu Linux 16.04 ESM.

USN-5080-2: Libgcrypt vulnerabilities

=========================================================================
Ubuntu Security Notice USN-5080-2
September 16, 2021

libgcrypt20 vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 16.04 ESM

Summary:

Libgcrypt could be made to expose sensitive information.

Software Description:
- libgcrypt20: LGPL Crypto library

Details:

USN-5080-1 fixed several vulnerabilities in Libgcrypt. This update provides
the corresponding update for Ubuntu 16.04 ESM.

Original advisory details:

It was discovered that Libgcrypt incorrectly handled ElGamal encryption. An
attacker could possibly use this issue to recover sensitive information.

Update instructions:

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

Ubuntu 16.04 ESM:
libgcrypt20 1.6.5-2ubuntu0.6+esm1

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

References:
  https://ubuntu.com/security/notices/USN-5080-2
  https://ubuntu.com/security/notices/USN-5080-1
CVE-2021-33560, CVE-2021-40528