CVE-2021-43172

NLnet Labs Routinator prior to 0.10.2 happily processes a chain of RRDP
repositories of infinite length causing it to never finish a validation
run. In RPKI, a CA can choose the RRDP repository it wishes to publish its
data in. By continuously generating a new child CA that only consists of
another CA using a different RRDP repository, a malicious CA can create a
chain of CAs of de-facto infinite length. Routinator prior to version
0.10.2 did not contain a limit on the length of such a chain and will
therefore continue to process this chain forever. As a result, the
validation run will never finish, leading to Routinator continuing to serve
the old data set or, if in the initial validation run directly after
starting, never serve any data at all.