Vixie Cron before 4.1-r10 on Gentoo Linux is installed with insecure permissions, which allows local users to cause a denial of service (cron failure) by creating hard links, which results in a failed st_nlink check in database.c.

From Red Hat Security Advisory 2007:0345 :

Updated vixie-cron packages that fix a denial of service issue are now available.

This update has been rated as having moderate security impact by the Red Hat Security Response Team.

The vixie-cron package contains the Vixie version of cron. Cron is a standard UNIX daemon that runs specified programs at scheduled times.

Raphael Marichez discovered a denial of service bug in the way vixie-cron verifies crontab file integrity. A local user with the ability to create a hardlink to /etc/crontab can prevent vixie-cron from executing certain system cron jobs. (CVE-2007-1856)

All users of vixie-cron should upgrade to these updated packages, which contain a backported patch to correct this issue.

Raphael Marichez discovered a denial of service bug in the way vixie-cron verifies crontab file integrity. A local user with the ability to create a hardlink to /etc/crontab can prevent vixie-cron from executing certain system cron jobs. (CVE-2007-1856)

Problems addressed by these patches :

I    Arbitrary code execution and denial of service vulnerabilities

     This release fixes a security vulnerability that could allow a      guest operating system user with administrative privileges to cause      memory corruption in a host process, and thus potentially execute      arbitrary code on the host. (CVE-2007-4496)

     This release fixes a denial of service vulnerability that could      allow a guest operating system to cause a host process to become      unresponsive or exit unexpectedly. (CVE-2007-4497)

     Thanks to Rafal Wojtczvk of McAfee for identifying and reporting      these issues.

II   Hosted products DHCP security vulnerabilities addressed

     This release fixes several vulnerabilities in the DHCP server      that could enable a specially crafted packets to gain system-level      privileges. (CVE-2007-0061, CVE-2007-0062, CVE-2007-0063)

     Thanks to Neel Mehta and Ryan Smith of the IBM Internet Security      Systems X-Force for discovering and researching these      vulnerabilities.

III  Windows based hosted product vulnerability in      IntraProcessLogging.dll and vielib.dll.

     This release fixes a security vulnerability that could allow a      malicious remote user to exploit the library file      IntraProcessLogging.dll to overwrite files in a system.
     (CVE-2007-4059)

     This release fixes a security vulnerability that could allow a      malicious remote user to exploit the library file vielib.dll to      overwrite files in a system. (CVE-2007-4155)

     Thanks to the Goodfellas Security Research Team for discovering and      researching these vulnerabilities.

IV  Escalation of privileges on Windows hosted systems

     This release fixes a security vulnerability in which Workstation      was starting registered Windows services in an insecure manner.
     This vulnerability could allow a malicious user to escalate user      privileges.

     Thanks to Foundstone for discovering this vulnerability.

V    Potential denial of service using VMware Player

     This release fixes a problem that prevented VMware Player from      launching. This problem was accompanied by the error message VMware      Player unrecoverable error: (player) Exception 0xc0000005 (access      violation) has occurred.

VI   ESX Service Console updates

a.   Service console package Samba, has been updated to address the      following issues :

     Various bugs were found in NDR parsing, used to decode MS-RPC      requests in Samba. A remote attacker could have sent carefully      crafted requests causing a heap overflow, which may have led to the      ability to execute arbitrary code on the server. (CVE-2007-2446)

     Unescaped user input parameters were being passed as arguments to      /bin/sh. A remote, authenticated, user could have triggered this      flaw and executed arbitrary code on the server. Additionally, this      flaw could be triggered by a remote unauthenticated user if Samba      was configured to use the non-default username map script option.
     (CVE-2007-2447)

     Thanks to the Samba developers, TippingPoint, and iDefense for      identifying and reporting these issues.

     Note: These issues only affect the service console network, and are      not remote vulnerabilities for ESX Server hosts that have been set      up with the security best practices provided by VMware.
     http://www.vmware.com/resources/techresources/726

b.   Updated bind package for the service console fixes a flaw with the      way ISC BIND processed certain DNS query responses.

     ISC BIND (Berkeley Internet Name Domain) is an implementation of      the DNS (Domain Name System) protocols. Under some circumstances, a      malicious remote user could launch a Denial-of-Service attack on      ESX Server hosts that had enabled DNSSEC validation.
     (CVE-2007-0494)

     Note: These issues only affect the service console network, and are      not remote vulnerabilities for ESX Server hosts that have been set      up with the security best practices provided by VMware.
     http://www.vmware.com/resources/techresources/726

c.   This patch provides updated service console package krb5 update.

     The Common Vulnerabilities and Exposures project (cve.mitre.org)      assigned the names CVE-2007-2442, CVE-2007-2443, and CVE-2007-2798      to these security issues.

     Thanks to Wei Wang of McAfee Avert Labs discovered these      vulnerabilities.

     Note: The VMware service console does not provide the kadmind      binary, and is not affected by these issues, but a update has been      provided for completeness.

d.   Service console update for vixie-cron

     This patch provides an updated service console package vixie-cron.
     Cron is a standard UNIX daemon that runs specified programs at      scheduled times.

     A denial of service issue was found in the way vixie-cron verified      crontab file integrity. A local user with the ability to create a      hardlink to /etc/crontab could potentially prevent vixie-cron from      executing certain system cron jobs. (CVE-2007-1856)

     Thanks to Raphael Marichez for identifying this issue.

e.   Service console update for shadow-utils

     This patch provides an updated shadow-utils package.  A new      user's mailbox, when created, could have random permissions for a      short period. This could enable a local malicious user to      read or modify the mailbox. (CVE-2006-1174)

f.  Service console update for OpenLDAP

     This patch provides a updated OpenLDAP package. A flaw could      allow users with selfwrite access to modify the distinguished      name of any user, instead of being limited to modify only      their own distinguished name. (CVE-2006-4600)

g.   Service console update for PAM

     This patch provides an updated PAM package A vulnerability was      found that could allow console users with access to certain device      files to cause damage to recordable CD drives. Certain file      permissions have now been modified to disallow access.
     (CVE-2004-0813)

     A flaw was found with console device permissions. It was possible      for various console devices to retain ownership of the previoius      console user after logging out, which could result in leakage of      information to an unauthorized user. (CVE-2007-1716)

h.   Service console update for GCC

     This patch provides security fixes for the service console GNU      Compiler Collection (GCC) packages that include C, C++, Java,      Fortran 77, Objective C, and Ada 95 GNU compilers and related      support libraries.

     A flaw was found in the fastjar utility that could potentially      allow a malicious user to create a JAR file which, if unpacked      using fastjar, could write to any file that an authorized user had      write access to. (CVE-2006-3619)

     Thanks to J&uuml;rgen Weigert for identifying this issue.

i.   Service Console update for GDB

     This patch provides a security fix for the service console GNU      debugger (GDB).  Various vulnerabilities were found in GDB. These      vulnerabilities may allow a malicious user to deceive a user into      loading debugging information into GDB, enabling the execution of      arbitrary code with the privileges of the user. (CVE-2006-4146)

By setting hard links to /etc/crontab users were able to prevent cron from running scheduled jobs. (CVE-2007-1856)

A re-emerged symlink bug allowed users to edit the crontab of other users. (CVE-2005-1038)

This is a reissue of the SLES10 update after Service Pack 1, since Service Pack 1 merge lost some of the fixes in the cron package.

By setting hard links to /etc/crontab users were able to prevent cron from running scheduled jobs. (CVE-2007-1856)

A re-emerged symlink bug allowed users to edit the crontab of other users. (CVE-2005-1038)

Raphael Marichez discovered a denial of service bug in how vixie-cron verifies crontab file integrity. A local user with the ability to create a hardlink to /etc/crontab could prevent vixie-cron from executing certain system cron jobs.

The updated packages have been patched to correct this issue.

By setting hard links to /etc/crontab users were able to prevent cron from running scheduled jobs (CVE-2007-1856).

A re-emerged symlink bug allowed users to edit the crontab of other users (CVE-2005-1038).

Updated vixie-cron packages that fix a denial of service issue are now available.

This update has been rated as having moderate security impact by the Red Hat Security Response Team.

The vixie-cron package contains the Vixie version of cron. Cron is a standard UNIX daemon that runs specified programs at scheduled times.

Raphael Marichez discovered a denial of service bug in the way vixie-cron verifies crontab file integrity. A local user with the ability to create a hardlink to /etc/crontab can prevent vixie-cron from executing certain system cron jobs. (CVE-2007-1856)

All users of vixie-cron should upgrade to these updated packages, which contain a backported patch to correct this issue.

The remote host is affected by the vulnerability described in GLSA-200704-11 (Vixie Cron: Denial of Service)

    During an internal audit, Raphael Marichez of the Gentoo Linux Security     Team found that Vixie Cron has weak permissions set on Gentoo, allowing     for a local user to create hard links to system and users cron files,     while a st_nlink check in database.c will generate a superfluous error.
  Impact :

    Depending on the partitioning scheme and the 'cron' group membership, a     malicious local user can create hard links to system or users cron     files that will trigger the st_link safety check and prevent the     targeted cron file from being run from the next restart or database     reload.
  Workaround :

    There is no known workaround at this time.

ID	Name	Product	Family	Severity
67493	Oracle Linux 3 / 4 / 5 : vixie-cron (ELSA-2007-0345)	Nessus	Oracle Linux Local Security Checks	low
60186	Scientific Linux Security Update : vixie-cron on SL5.x, SL4.x, SL3.x i386/x86_64	Nessus	Scientific Linux Local Security Checks	low
40370	VMSA-2007-0006 : Critical security updates for all supported versions of VMware ESX Server, VMware Server, VMware Workstation, VMware ACE, and VMware Player	Nessus	VMware ESX Local Security Checks	critical
29408	SuSE 10 Security Update : cron (ZYPP Patch Number 3831)	Nessus	SuSE Local Security Checks	low
29407	SuSE 10 Security Update : cron (ZYPP Patch Number 3093)	Nessus	SuSE Local Security Checks	low
29201	Mandrake Linux Security Advisory : vixie-cron (MDKSA-2007:234)	Nessus	Mandriva Local Security Checks	low
27190	openSUSE 10 Security Update : cron (cron-3092)	Nessus	SuSE Local Security Checks	low
25267	RHEL 3 / 4 / 5 : vixie-cron (RHSA-2007:0345)	Nessus	Red Hat Local Security Checks	low
25254	CentOS 3 / 4 / 5 : vixie-cron (CESA-2007:0345)	Nessus	CentOS Local Security Checks	low
25056	GLSA-200704-11 : Vixie Cron: Denial of Service	Nessus	Gentoo Local Security Checks	low

Detections

Analytics

CVE-2007-1856

high

Tenable Plugins

low

low

critical

low

low

low

low

low

low

low