Trending CVEs for the Week of October 14th, 2019
- Oct 17, 2019
- Michael Tucker
A flaw was found in the way sudo implemented running commands with arbitrary user ID. If a sudoers entry is written to allow the attacker to run a command as any user except root, this flaw can be used by the attacker to bypass that restriction.
This vulnerability only affects configurations of sudo that have a runas user list that includes an exclusion of root. The most simple example is:
someuser ALL=(ALL, !root) /usr/bin/somecommand
The exclusion is specified using an excalamation mark (!). In this example, the “root” user is specified by name. The root user may also be identified in other ways, such as by user id:
someuser ALL=(ALL, !#0) /usr/bin/somecommand
or by reference to a runas alias:
Runas_Alias MYGROUP = root, adminuser someuser ALL=(ALL, !MYGROUP) /usr/bin/somecommand
To ensure your sudoers configuration is not affected by this vulnerability, we recommend examining each sudoers entry that includes the `!` character in the runas specification, to ensure that the root user is not among the exclusions. These can be found in the /etc/sudoers file or files under /etc/sudoers.d.