There are 2 open security issues in bullseye.
2 issues left for the package maintainer to handle:
A vulnerability was found in Exim and classified as problematic. This issue affects some unknown processing of the component Regex Handler. The manipulation leads to use after free. The name of the patch is 4e9ed49f8f12eb331b29bd5b6dc3693c520fddc2. It is recommended to apply a patch to fix this issue. The identifier VDB-211073 was assigned to this vulnerability.
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.
You can find information about how to handle these issues in the security team's documentation.