USN-6455-2: Exim regression

USN-6455-1 fixed vulnerabilities in Exim. The fix for CVE-2023-42117 introduced a regression on Ubuntu 22.04 LTS that resulted in certain connections logging a Taint mismatch error. This update fixes the problem. We apologize for the inconvenience. Original advisory details: It was discovered that Exim incorrectly handled validation of user-supplied data, which could lead to memory corruption. A remote attacker could possibly use this issue to execute arbitrary code. (CVE-2023-42117) It was discovered that Exim incorrectly handled validation of user-supplied data, which could lead to an out-of-bounds read. An attacker could possibly use this issue to expose sensitive information. (CVE-2023-42119)