Subject: [ASA-201910-9] sudo: privilege escalation

Arch Linux Security Advisory ASA-201910-9
=========================================

Severity: High
Date    : 2019-10-16
CVE-ID  : CVE-2019-14287
Package : sudo
Type    : privilege escalation
Remote  : No
Link    : https://security.archlinux.org/AVG-1047

Summary
=======

The package sudo before version 1.8.28-1 is vulnerable to privilege
escalation.

Resolution
==========

Upgrade to 1.8.28-1.

# pacman -Syu "sudo>=1.8.28-1"

The problem has been fixed upstream in version 1.8.28.

Workaround
==========

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.

Description
===========

A flaw was found in the way sudo prior to 1.8.28 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.

Impact
======

A local attacker is able to gain root privileges when sudo is
configured to have a runas user list that includes an exclusion of
root.

References
==========

https://www.sudo.ws/alerts/minus_1_uid.html
https://www.sudo.ws/repos/sudo/rev/83db8dba09e7
https://security.archlinux.org/CVE-2019-14287