CVE-2026-52817: Improper Neutralization of Argument Delimiters in a Command

Linuxfabrik Monitoring Plugins provides monitoring plugins for Icinga, Nagios, and related systems. Prior to version 5.1.0, the shipped assets/sudoers/Debian.sudoers policy allowed the nagios or icinga account to execute /usr/bin/apt-get as root without restricting its arguments. An attacker who already controls that monitoring account can supply the APT::Update::Pre-Invoke option to execute an arbitrary command while apt-get runs with root privileges, resulting in a root shell and complete compromise of the host. The vulnerable rule supports the check-plugins/deb-updates/deb-updates plugin, but it authorized arbitrary apt-get argument sequences rather than only the required apt-get update --quiet 2 command. This issue is fixed in version 5.1.0.