Add CVE-2019-19921/runc

Details on the issue seem not present. The CVE was mentioned in
https://lore.kernel.org/stable/20191230052036.8765-2-cyphar@cyphar.com/
and cross checking with containers
https://github.com/opencontainers/runc/pull/2190 is found, but without
information on the vulnerability. It seems to be related to an audit
performed by Cure53 as per
https://github.com/opencontainers/runc/pull/2190/commits/36268ea7e4a7bb02c9df1954a1d3d912e568ba69
.