Debian Security Advisory

DLA-1723-1 cron -- LTS security update

Date Reported:
21 Mar 2019
Affected Packages:
Security database references:
In the Debian bugtracking system: Bug 809167.
In Mitre's CVE dictionary: CVE-2017-9525, CVE-2019-9704, CVE-2019-9705, CVE-2019-9706.
More information:

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

  • 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 8 Jessie, these problems have been fixed in version 3.0pl1-127+deb8u2.

We recommend that you upgrade your cron packages.

Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: