ELA-103-1 cron security update

several DoS fixes, root escalation fix

Related CVEs CVE-2017-9525 CVE-2019-9704 CVE-2019-9705 CVE-2019-9706

Various security problems have been discovered in Debian’s CRON scheduler.

CVE-2017-9525: Fix group crontab to root escalation via the Debian package’s postinst script as described by Alexander Peslyak (Solar Designer) in http://www.openwall.com/lists/oss-security/2017/06/08/3

CVE-2019-9704: DoS: Fix unchecked return of calloc(). Florian Weimer discovered that a missing check for the return value of calloc() could crash the daemon, which could be triggered by a very large crontab created by a user.

CVE-2019-9705: Enforce maximum crontab line count of 1000 to prevent a malicious user from creating an excessivly large crontab. The daemon will log a warning for existing files, and crontab(1) will refuse to create new ones.

CVE-2019-9706: A user reported a use-after-free condition in the cron daemon, leading to a possible Denial-of-Service scenario by crashing the daemon.

For Debian 7 Wheezy, these problems have been fixed in version 3.0pl1-124+deb7u1.

We recommend that you upgrade your cron packages.

Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/