An OpenSSL security update has been released for Ubuntu Linux 16.04 LTS and 18.04 LTS.

[USN-6435-1] OpenSSL vulnerabilities

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Ubuntu Security Notice USN-6435-1
October 18, 2023

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

- Ubuntu 18.04 LTS (Available with Ubuntu Pro)
- Ubuntu 16.04 LTS (Available with Ubuntu Pro)

Summary:

OpenSSL could be made to consume resources and cause long delays
if it processed certain input.

Software Description:
- openssl: Secure Socket Layer (SSL) cryptographic library and tools

Details:

It was discovered that OpenSSL incorrectly handled excessively large
Diffie-Hellman parameters. An attacker could possibly use this issue
to cause a denial of service. (CVE-2023-3446)

Bernd Edlinger discovered that OpenSSL incorrectly handled excessively
large Diffie-Hellman parameters. An attacker could possibly use this
issue to cause a denial of service. (CVE-2023-3817)

Update instructions:

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

Ubuntu 18.04 LTS (Available with Ubuntu Pro):
  libssl1.1                        1.1.1-1ubuntu2.1~18.04.23+esm1
  openssl                         1.1.1-1ubuntu2.1~18.04.23+esm1

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
  libssl1.0.0                     1.0.2g-1ubuntu4.20+esm10
  openssl                         1.0.2g-1ubuntu4.20+esm10

After a standard system update you need to reboot your computer to make
all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-6435-1
  CVE-2023-3446, CVE-2023-3817