Bug 600097 (CVE-2010-2024)

Summary: CVE-2010-2024 exim: race condition when MBX locking is enabled
Product: [Other] Security Response Reporter: Vincent Danen <vdanen>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED WONTFIX QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: dwmw2, mlichvar
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Fixed In Version: Doc Type: Bug Fix
Doc Text:
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Clone Of: Environment:
Last Closed: 2015-07-29 14:44:43 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:

Description Vincent Danen 2010-06-03 22:51:27 UTC
Dan Rosenberg reported that when MBX locking is enabled in exim, local users could exploit a race condition to change permissions of other non-root users' files.  This could lead to a denial of service, to create new files owned by other users in unauthorized locations, or to possibly escalate privileges.

Further information is available from the upstream bug report [1] and this has
been fixed upstream in exim 4.72 [2].

[1] http://bugs.exim.org/show_bug.cgi?id=989
[2] http://vcs.exim.org/viewvc/exim/exim-src/src/transports/appendfile.c?r1=1.25&r2=1.26

While exim is built to support the MBX format, it is not the default for local mail delivery (Unix mailbox support is the default).  This will only affect users that use the "mbx_format" option in the appendfile transport.

Comment 1 Vincent Danen 2010-06-03 23:09:40 UTC

The Red Hat Security Response Team has rated this issue as having low security impact.  While support for the MBX mailbox format is compiled into Exim, it is not used by default.  MBX mailboxes are only useful when used with UW-IMAP or the Pine mail client, neither of which are provided with Red Hat Enterprise Linux.  If the MBX format is used, this issue can be worked around by specifying "use_fcntl_lock" rather than "use_mbx_lock".  We therefore have no plans to fix this flaw in Red Hat Enterprise Linux 4 or 5.

Comment 2 Fedora Update System 2010-06-03 23:51:59 UTC
exim-4.72-1.fc12 has been submitted as an update for Fedora 12.

Comment 3 Fedora Update System 2010-06-03 23:53:02 UTC
exim-4.72-1.fc13 has been submitted as an update for Fedora 13.

Comment 4 Fedora Update System 2010-06-08 19:33:31 UTC
exim-4.72-1.fc12 has been pushed to the Fedora 12 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 5 Fedora Update System 2010-06-08 19:39:42 UTC
exim-4.72-1.fc13 has been pushed to the Fedora 13 stable repository.  If problems still persist, please make note of it in this bug report.