Several vulnerabilities have been discovered in the interpreter for the
Ruby language and the Rubygems included, which may result on result in
XML roundtrip attacks, the execution of arbitrary code, information
disclosure, StartTLS stripping in IMAP or denial of service.
For the oldstable distribution (buster), these problems have been fixed
in version 2.5.5-3+deb10u4.
We recommend that you upgrade your ruby2.5 packages.