FreeBSD -- Resource exhaustion due to sessions stuck in LAST_ACK state

2015-07-21T00:00:00
ID 0C064C43-600A-11E6-A6C3-14DAE9D210B8
Type freebsd
Reporter FreeBSD
Modified 2015-07-21T00:00:00

Description

Problem Description: TCP connections transitioning to the LAST_ACK state can become permanently stuck due to mishandling of protocol state in certain situations, which in turn can lead to accumulated consumption and eventual exhaustion of system resources, such as mbufs and sockets. Impact: An attacker who can repeatedly establish TCP connections to a victim system (for instance, a Web server) could create many TCP connections that are stuck in LAST_ACK state and cause resource exhaustion, resulting in a denial of service condition. This may also happen in normal operation where no intentional attack is conducted, but an attacker who can send specifically crafted packets can trigger this more reliably.