The uipc system calls (uipc_syscalls.c) in OpenBSD 2.9 and 3.0 provide user mode return instead of versus rval kernel mode values to the fdrelease function, which allows local users to cause a denial of service and trigger a null dereference.

vi.recover in OpenBSD before 3.1 allows local users to remove arbitrary zero-byte files such as device nodes.

Buffer overflow in BSD line printer daemon (in.lpd or lpd) in various BSD-based operating systems allows remote attackers to execute arbitrary code via an incomplete print job followed by a request to display the printer queue.

fts routines in FreeBSD 4.3 and earlier, NetBSD before 1.5.2, and OpenBSD 2.9 and earlier can be forced to change (chdir) into a different directory than intended when the directory above the current directory is moved, which could cause scripts to perform dangerous actions on the wrong directories.

Buffer overflow in BSD-based telnetd telnet daemon on various operating systems allows remote attackers to execute arbitrary commands via a set of options including AYT (Are You There), which is not properly handled by the telrcv function.

Multiple TCP implementations could allow remote attackers to cause a denial of service (bandwidth and CPU exhaustion) by setting the maximum segment size (MSS) to a very small number and requesting large amounts of data, which generates more packets with less TCP-level data that amplify network traffic and consume more server CPU to process.

readline prior to 4.1, in OpenBSD 2.8 and earlier, creates history files with insecure permissions, which allows a local attacker to recover potentially sensitive information via readline history files.

IPFilter 3.4.16 and earlier does not include sufficient session information in its cache, which allows remote attackers to bypass access restrictions by sending fragmented packets to a restricted port after sending unfragmented packets to an unrestricted port.

Buffer overflows in BSD-based FTP servers allows remote attackers to execute arbitrary commands via a long pattern string containing a {} sequence, as seen in (1) g_opendir, (2) g_lstat, (3) g_stat, and (4) the glob0 buffer as used in the glob functions glob2 and glob3.

Race condition in OpenBSD VFS allows local users to cause a denial of service (kernel panic) by (1) creating a pipe in one thread and causing another thread to set one of the file descriptors to NULL via a close, or (2) calling dup2 on a file descriptor in one process, then setting the descriptor to NULL via a close in another process that is created via rfork.