The nfs-utils package contains the rpc.mountd program, which implements the NFS mount protocol.
A flaw was discovered in versions of rpc.mountd in nfs-utils versions after 1.0.3 and prior to 1.0.6. When mounting a directory, rpc.mountd could crash if the reverse lookup of the client in DNS failed to match the forward lookup. An attacker who has the ability to mount remote directories from a server could make use of this flaw to cause a denial of service by making rpc.mountd crash.
Users are advised to upgrade to these updated packages, which contain nfs-utils 1.0.6 and is not vulnerable to this issue.
NOTE: Red Hat Enterprise Linux 2.1 includes a version of rpc.mountd that is not vulnerable to this issue.