Debian Security Advisory

DLA-2801-1 cron -- LTS security update

Date Reported:
30 Oct 2021
Affected Packages:
Security database references:
In the Debian bugtracking system: Bug 809167, Bug 809167.
In Mitre's CVE dictionary: CVE-2017-9525, CVE-2019-9704, CVE-2019-9705, CVE-2019-9706.
More information:

Several security problems have been fixed in the cron daemon.

  • CVE-2017-9525

    Fix group crontab to root escalation via postinst.

  • CVE-2019-9704

    A very large crontab created by a user could crash the daemon.

  • CVE-2019-9705

    Enforce maximum crontab line count of 10000 to prevent a malicious user from creating an excessivly large crontab.

  • CVE-2019-9706

    Fix for possible DoS by use-after-free.

  • Additionally, a bypass of /etc/cron.{allow,deny} on failure to open has been fixed. If these files exist, then they must be readable by the user executing crontab(1). Users will now be denied by default if they aren't.

For Debian 9 stretch, these problems have been fixed in version 3.0pl1-128+deb9u2.

We recommend that you upgrade your cron packages.

For the detailed security status of cron please refer to its security tracker page at:

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