A race condition was found in the way the Linux kernel’s memory subsystem handled the copy-on-write (COW) breakage of private read-only memory mappings. An unprivileged local user could use this flaw to gain write access to otherwise read-only memory mappings and thus increase their privileges on the system. An exploit using this technique has been found in the wild.
All Linux users are recommended to patch and update the system. Patches are available here