CVE-2017-3224

Open Shortest Path First (OSPF) protocol implementations may improperly
determine Link State Advertisement (LSA) recency for LSAs with
MaxSequenceNumber. According to RFC 2328 section 13.1, for two instances of
the same LSA, recency is determined by first comparing sequence numbers,
then checksums, and finally MaxAge. In a case where the sequence numbers
are the same, the LSA with the larger checksum is considered more recent,
and will not be flushed from the Link State Database (LSDB). Since the RFC
does not explicitly state that the values of links carried by a LSA must be
the same when prematurely aging a self-originating LSA with
MaxSequenceNumber, it is possible in vulnerable OSPF implementations for an
attacker to craft a LSA with MaxSequenceNumber and invalid links that will
result in a larger checksum and thus a ‘newer’ LSA that will not be flushed
from the LSDB. Propagation of the crafted LSA can result in the erasure or
alteration of the routing tables of routers within the routing domain,
creating a denial of service condition or the re-routing of traffic on the
network. CVE-2017-3224 has been reserved for Quagga and downstream
implementations (SUSE, openSUSE, and Red Hat packages).

Bugs

• <https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=871617&gt;

Notes