DescriptionA file descriptor leak issue was found in the runc package. While a user performs `O_CLOEXEC` all file descriptors before executing the container code, the file descriptor is open when performing `setcwd(2)`, which means that the reference can be kept alive in the container by configuring the working directory to be a path resolved through the file descriptor. The non-dumpable bit is unset after `execve`, meaning there are multiple ways to attack this other than bad configurations. The only way to defend against it entirely is to close all unneeded file descriptors.A file descriptor leak issue was found in the runc package. While a user performs O_CLOEXEC all file descriptors before executing the container code, the file descriptor is open when performing setcwd(2), which means that the reference can be kept alive in the container by configuring the working directory to be a path resolved through the file descriptor. The non-dumpable bit is unset after execve, meaning there are multiple ways to attack this other than bad configurations. The only way to defend against it entirely is to close all unneeded file descriptors.