In the cron package through 3.0pl1-128 on Debian, and through 3.0pl1-128ubuntu2 on Ubuntu, the postinst maintainer script allows for group-crontab-to-root privilege escalation via symlink attacks against unsafe usage of the chown and chmod programs.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - In the cron package through 3.0pl1-128 on Debian, and through 3.0pl1-128ubuntu2 on Ubuntu, the postinst     maintainer script allows for group-crontab-to-root privilege escalation via symlink attacks against unsafe     usage of the chown and chmod programs. (CVE-2017-9525)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote Ubuntu 16.04 ESM / 18.04 LTS host has a package installed that is affected by a vulnerability as referenced in the USN-5259-3 advisory.

    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.



Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Ubuntu 18.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-5259-2 advisory.

    USN-5259-1 fixed several vulnerabilities in Cron. This update provides the corresponding update for Ubuntu     18.04 LTS.



Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 16.04 ESM host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-5259-1 advisory.

    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)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Debian 9 host has a package installed that is affected by multiple vulnerabilities as referenced in the dla-2801 advisory.

  - In the cron package through 3.0pl1-128 on Debian, and through 3.0pl1-128ubuntu2 on Ubuntu, the postinst     maintainer script allows for group-crontab-to-root privilege escalation via symlink attacks against unsafe     usage of the chown and chmod programs. (CVE-2017-9525)

  - Vixie Cron before the 3.0pl1-133 Debian package allows local users to cause a denial of service (daemon     crash) via a large crontab file because the calloc return value is not checked. (CVE-2019-9704)

  - Vixie Cron before the 3.0pl1-133 Debian package allows local users to cause a denial of service (memory     consumption) via a large crontab file because an unlimited number of lines is accepted. (CVE-2019-9705)

  - Vixie Cron before the 3.0pl1-133 Debian package allows local users to cause a denial of service (use-     after-free and daemon crash) because of a force_rescan_user error. (CVE-2019-9706)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

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

We recommend that you upgrade your cron packages.

NOTE: Tenable Network Security has extracted the preceding description block directly from the DLA security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Severity
221564	Linux Distros Unpatched Vulnerability : CVE-2017-9525	Nessus	Misc.	medium
160980	Ubuntu 16.04 ESM / 18.04 LTS : Cron regression (USN-5259-3)	Nessus	Ubuntu Local Security Checks	medium
160668	Ubuntu 18.04 LTS : Cron vulnerabilities (USN-5259-2)	Nessus	Ubuntu Local Security Checks	medium
157299	Ubuntu 16.04 ESM : Cron vulnerabilities (USN-5259-1)	Nessus	Ubuntu Local Security Checks	medium
154747	Debian DLA-2801-1 : cron - LTS security update	Nessus	Debian Local Security Checks	medium
123017	Debian DLA-1723-1 : cron security update	Nessus	Debian Local Security Checks	medium

Detections

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CVE-2017-9525

medium

Tenable Plugins

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medium

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medium