[USN-5259-3] Cron regression


========================================================================== Ubuntu Security Notice USN-5259-3 May 11, 2022
cron regression ==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:
– Ubuntu 18.04 LTS – Ubuntu 16.04 ESM
Summary:
USN-5259-1 and USN-5259-2 introduced a regression in Cron.
Software Description: – cron: process scheduling daemon
Details:
USN-5259-1 and USN-5259-2 fixed vulnerabilities in Cron. Unfortunately that update was incomplete and could introduce a regression. This update fixes the problem.
We apologize for the inconvenience.
Original advisory details:
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)
Update instructions:
The problem can be corrected by updating your system to the following package versions:
Ubuntu 18.04 LTS: cron 3.0pl1-128.1ubuntu1.2
Ubuntu 16.04 ESM: cron 3.0pl1-128ubuntu2+esm2
In general, a standard system update will make all the necessary changes.
References: ubuntu.com/security/notices/USN-5259-1 ubuntu.com/security/notices/USN-5259-2 ubuntu.com/security/notices/USN-5259-3 launchpad.net/bugs/1971895 CVE-2017-9525
Package Information: launchpad.net/ubuntu/+source/cron/3.0pl1-128.1ubuntu1.2