One of the most renowned and widely-used Linux commands — the Sudo command — has a security flaw, which allows Linux users to run commands as root even when their permission to do so has been denied. The vulnerability was discovered by Joe Vennix of Apple Information Security.
The Sudo Flaw
It is suggested that when a Linux user allows for the Sudo system command to run tasks, they can run those tasks as root even when the permission for the same is not granted.
For those who don’t know, the Linux Sudo command (or Superuser do) is an important command that provides users with ‘elevated privileges.’ The elevated privileges allow for various administrative tasks that users might not be able to perform otherwise.
This can primarily be used to run commands as root but with the required permission of course. The permission involves the use of a special UID allotted to every user. This means that the user’s sudoer entry has the keyword “All” in the Runus application.
Additionally, the Sudo command allows users to run tasks as another user.
However, the new flaw is able to access the UID of another user as either “-1” or “4294967295” in the Sudo command. It provides Linux users, specifically malign users, unauthorized access to run the commands as root.
Since the vulnerability allows for access to run the commands, it treats the UID of the other user (which is mostly 0) as 0 when in reality -1 is entered.
Furthermore, as the Sudo command (with -1) is not registered in the password database, PAM session modules won’t be able to run.
One thing worth noting is that the vulnerability works only when the user is given access to any command via the sudoer configuration file. Hence, most of the Linux servers have remained unaffected.
The Sudo Command Flaw Fix
The Sudo command flaw has been patched as part of the Sudo update version 1.8.28. Linux users who have Sudo versions prior to the new version need to update to avoid the vulnerability.