The SYN cache (syncache) and SYN cookie (syncookie) mechanism in FreeBSD 4.5 and earlier allows remote attackers to cause a denial of service (crash) (1) via a SYN packet that is accepted using syncookies that causes a null pointer to be referenced for the sockets TCP options, or (2) by killing and restarting a process that listens on the same socket, which does not properly clear the old inpcb pointer on restart.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Freebsd | Freebsd | 4.5-release (including) | 4.5-release (including) |
| Freebsd | Freebsd | 4.5-stable (including) | 4.5-stable (including) |