Several vulnerabilities have been discovered in the Rubygems included in the interpreter for the Ruby language, which may result in denial of service or the execution of arbitrary code.
For the stable distribution (stretch), these problems have been fixed in version 2.3.3-1+deb9u6.
We recommend that you upgrade your ruby2.3 packages.
Further information about Debian Security Advisories, how to apply these updates to your system and frequently asked questions can be found at: https://www.debian.org/security/