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             AUSCERT External Security Bulletin Redistribution

                              ESB-2022.2280.2
                        USN-5259-3: Cron regression
                                12 May 2022

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Cron
Publisher:         Ubuntu
Operating System:  Ubuntu
Resolution:        Patch/Upgrade
CVE Names:         CVE-2019-9706 CVE-2019-9705 CVE-2019-9704
                   CVE-2017-9525  

Original Bulletin: 
   https://ubuntu.com/security/notices/USN-5259-3

Comment: CVSS (Max):  6.7 CVE-2017-9525 (CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H)
         CVSS Source: NVD
         Calculator:  https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Revision History:  May 12 2022: Resend following GPG key renewal
                   May 11 2022: Initial Release

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USN-5259-3: Cron regression
11 May 2022

USN-5259-1 and USN-5259-2 introduced a regression in Cron.
Releases

  o Ubuntu 18.04 LTS
  o Ubuntu 16.04 ESM

Packages

  o 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

  o cron - 3.0pl1-128.1ubuntu1.2

Ubuntu 16.04

  o cron - 3.0pl1-128ubuntu2+esm2
    Available with UA Infra or UA Desktop

In general, a standard system update will make all the necessary changes.

References

  o CVE-2017-9525
  o https://ubuntu.com/security/notices/USN-5259-2
  o https://launchpad.net/bugs/1971895

Related notices

  o USN-5259-1 : cron
  o USN-5259-2 : cron

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