Debian (and Ubuntu as a downstream) patched out issues already: https://www.debian.org/security/2018/dsa-4104
[0]: https://landave.io/2018/01/7-zip-multiple-memory-corruptions...
https://www.debian.org/security/faq#contrib
That would have to wait for the maintainer to upload a new version and get it into a stable release.
here's the status of your DSA's vulnerability in Ubuntu: https://people.canonical.com/~ubuntu-security/cve/2017/CVE-2...
Here's the status of the post's vulnerability in Ubuntu: https://people.canonical.com/~ubuntu-security/cve/2018/CVE-2...