In the cron package through 3.0pl1-128 on Debian, and through 3.0pl1-128ubuntu2 on Ubuntu, the postinst maintainer script allows for group-crontab-to-root privilege escalation via symlink attacks against unsafe usage of the chown and chmod programs.

Affected: Ubuntu:Pro:16.04:LTS: cron

It was discovered that the postinst maintainer script in Cron unsafely handled file permissions during package install or update operations. An attacker could possibly use this issue to perform a privilege escalation attack. (CVE-2017-9525)

Florian Weimer discovered that Cron incorrectly handled certain memory operations during crontab file creation. An attacker could possibly use this issue to cause a denial of service. (CVE-2019-9704)

It was discovered that Cron incorrectly handled user input during crontab file creation. An attacker could possibly use this issue to cause a denial of service. (CVE-2019-9705)

It was discovered that Cron contained a use-after-free vulnerability in its force_rescan_user function. An attacker could possibly use this issue to cause a denial of service. (CVE-2019-9706)