A flaw in the kernels implementation of ptrace which could inadvertantly grant elevated permissions to an attacker who could abuse the relationship between tracer and the process being traced.

The mechanism used to link the process requesting the ptrace and the process being ptraced could allow a local user to obtain root level priviledges by creating an opportunity to abuse the frequently used pattern of dropping privileges and then execve a child with reduced privileges/permissions.

References: https://bugs.chromium.org/p/project-zero/issues/detail?id=1903 https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.1.17 https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6994eefb0053799d2e07cd140df6c2ea106c41ee https://github.com/torvalds/linux/commit/6994eefb0053799d2e07cd140df6c2ea106c41ee

Apache HTTP Server, with MPM event, worker or prefork, code executing in less-privileged child processes or threads (including scripts executed by an in-process scripting interpreter) could execute code with the privileges of the parent process (usually root) by manipulating the scoreboard.