==========================================================================
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