The icmp_send function in net/ipv4/icmp.c in the Linux kernel before 2.6.25, when configured as a router with a REJECT route, does not properly manage the Protocol Independent Destination Cache (aka DST) in some situations involving transmission of an ICMP Host Unreachable message, which allows remote attackers to cause a denial of service (connectivity outage) by sending a large series of packets to many destination IP addresses within this REJECT route, related to an "rt_cache leak."