Exim alternate configuration privilege escalation vulnerability

Overview

A vulnerability in the way that the Exim mail server handles configuration files may allow a local attacker to gain escalated privileges on an affected system.

Description

Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems connected to the Internet. If Exim is built without specifying the ALT_CONFIG_ROOT_ONLY configuration option, then the Exim user can invoke Exim with an arbitrary configuration file. The Exim developers note that this option is unspecified by default. Consequently, any ${run...} directives specified in that configuration file will be executed as root.

Note: this vulnerability has been reported being exploited in the wild.

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Impact

A local attacker with the ability to execute commands as the Exim user may be able to execute code with root privileges.

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Solution

We are currently unaware of a practical solution to this problem.

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Ensure that Exim is built with the ALT_CONFIG_ROOT_ONLY option enabled

The Exim developers note that this may result in a loss of functionality in certain cases where more than one configuration is in use. Specifically, the exim user will no longer be permitted to invoke Exim with an alternative configuration file and have it executed with root privileges.

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Vendor Information

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SUSE Linux Affected

Updated: December 13, 2010

Statement Date: December 13, 2010

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Vendor References

• <http://lists.opensuse.org/opensuse-security-announce/2010-12/msg00003.html&gt;

CVSS Metrics

Group	Score	Vector
Base
Temporal
Environmental

References

• <http://www.exim.org/lurker/message/20101207.215955.bb32d4f2.en.html&gt;
• <http://bugs.exim.org/show_bug.cgi?id=1044&gt;
• <https://bugzilla.redhat.com/show_bug.cgi?id=662012&gt;
• <http://lists.exim.org/lurker/message/20101209.172233.abcba158.en.html&gt;
• <http://lists.exim.org/lurker/message/20101213.140800.7c3bae4b.en.html&gt;

Acknowledgements

This vulnerability was discovered as a result of its exploitation in the wild. Sergey Kononenko provided confirmation and public analysis.

This document was written by Chad R Dougherty.

Other Information

CVE IDs:	CVE-2010-4345
Severity Metric:	13.54 Date Public: