[USN-6901-1] stunnel vulnerability

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==========================================================================
Ubuntu Security Notice USN-6901-1
July 18, 2024

stunnel vulnerability
==========================================================================

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

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

stunnel could allow unintended access to network services.

Software Description:
- stunnel4: Universal SSL tunnel for network daemons

Details:

It was discovered that stunnel did not properly validate client
certificates when configured to use both the redirect and verifyChain
options. A remote attacker could potentially use this issue to obtain
sensitive information by accessing the tunneled service.

Update instructions:

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

Ubuntu 20.04 LTS
stunnel4 3:5.56-1ubuntu0.2

Ubuntu 18.04 LTS
stunnel4 3:5.44-1ubuntu3+esm1
Available with Ubuntu Pro

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

References:
https://ubuntu.com/security/notices/USN-6901-1
CVE-2021-20230

Package Information:
https://launchpad.net/ubuntu/+source/stunnel4/3:5.56-1ubuntu0.2