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AUSCERT External Security Bulletin Redistribution
ESB-2014.0868
sendmail improper close-on-exec flag handling
4 June 2014
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AusCERT Security Bulletin Summary
---------------------------------
Product: sendmail
Publisher: FreeBSD
Operating System: FreeBSD
UNIX variants (UNIX, Linux, OSX)
Impact/Access: Reduced Security -- Existing Account
Resolution: Patch/Upgrade
Original Bulletin:
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-14:11.sendmail.asc
Comment: This advisory references vulnerabilities in products which run on
platforms other than FreeBSD. It is recommended that administrators
running sendmail check for an updated version of the software for
their operating system.
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FreeBSD-SA-14:11.sendmail Security Advisory
The FreeBSD Project
Topic: sendmail improper close-on-exec flag handling
Category: contrib
Module: sendmail
Announced: 2014-06-03
Affects: All supported versions of FreeBSD.
Corrected: 2014-05-26 15:35:11 UTC (stable/10, 10.0-STABLE)
2014-06-03 19:02:52 UTC (releng/10.0, 10.0-RELEASE-p4)
2014-05-26 20:10:00 UTC (stable/9, 9.3-PRERELEASE)
2014-06-03 19:03:11 UTC (releng/9.2, 9.2-RELEASE-p7)
2014-06-03 19:03:11 UTC (releng/9.1, 9.1-RELEASE-p14)
2014-05-26 15:30:27 UTC (stable/8, 8.4-STABLE)
2014-06-03 19:03:23 UTC (releng/8.4, 8.4-RELEASE-p11)
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:http://security.FreeBSD.org/>.
I. Background
FreeBSD includes sendmail(8), a general purpose internetwork mail
routing facility, as the default Mail Transfer Agent (MTA).
FreeBSD uses file descriptor as an abstract indicator for accessing a file.
Upon execve(2), file descriptors open in the calling process image remain
open in the new process image, except for those for which the close-on-exec
flag is set.
II. Problem Description
There is a programming error in sendmail(8) that prevented open file
descriptors have close-on-exec properly set. Consequently a subprocess
will be able to access all open files that the parent process have open.
III. Impact
A local user who can execute their own program for mail delivery will be
able to interfere with an open SMTP connection.
IV. Workaround
Do not allow untrusted users to specify programs for mail delivery, for
instance, procmail.
Systems that do not use sendmail(8) MTA are not affected.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.
2) To update your vulnerable system via a source code patch:
The following patches have been verified to apply to the applicable
FreeBSD release branches.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
# fetch http://security.FreeBSD.org/patches/SA-14:11/sendmail.patch
# fetch http://security.FreeBSD.org/patches/SA-14:11/sendmail.patch.asc
# gpg --verify sendmail.patch.asc
b) Apply the patch. Execute the following commands as root:
# cd /usr/src
# patch < /path/to/patch
c) Recompile the operating system using buildworld and installworld as
described in <URL:http://www.FreeBSD.org/handbook/makeworld.html>.
Restart the applicable daemons, or reboot the system.
3) To update your vulnerable system via a binary patch:
Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:
# freebsd-update fetch
# freebsd-update install
VI. Correction details
The following list contains the correction revision numbers for each
affected branch.
Branch/path Revision
- - -------------------------------------------------------------------------
stable/8/ r266693
releng/8.4/ r267019
stable/9/ r266711
releng/9.1/ r267018
releng/9.2/ r267018
stable/10/ r266692
releng/10.0/ r267017
- - -------------------------------------------------------------------------
To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:
# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base
Or visit the following URL, replacing NNNNNN with the revision number:
<URL:http://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>
VII. References
The latest revision of this advisory is available at
<URL:http://security.FreeBSD.org/advisories/FreeBSD-SA-14:11.sendmail.asc>
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