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ESB-2015.2551 - [Linux][BSD][OSX] OpenSMTPD: Execute arbitrary code/commands - Remote/unauthenticated

Date: 06 October 2015

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             AUSCERT External Security Bulletin Redistribution

                         OpenSMTPD 5.7.2 released
                              6 October 2015


        AusCERT Security Bulletin Summary

Product:           OpenSMTPD
Publisher:         OpenBSD
Operating System:  BSD variants
                   OS X
                   Linux variants
Impact/Access:     Execute Arbitrary Code/Commands -- Remote/Unauthenticated
                   Modify Arbitrary Files          -- Existing Account      
                   Denial of Service               -- Remote/Unauthenticated
                   Access Confidential Data        -- Remote/Unauthenticated
Resolution:        Patch/Upgrade

Original Bulletin:

Comment: This advisory references vulnerabilities in products which run on 
         platforms other than OpenBSD. It is recommended that administrators
         running OpenSMTPD check for an updated version of the software for 
         their operating system.

- --------------------------BEGIN INCLUDED TEXT--------------------

Subject: Announce: OpenSMTPD 5.7.2 released

OpenSMTPD 5.7.2 has just been released.

OpenSMTPD is a FREE implementation of the SMTP protocol with some common
extensions. It allows ordinary machines to exchange e-mails with systems
speaking the SMTP protocol. It implements a fairly large part of RFC5321
and can already cover a large range of use-cases.

It runs on OpenBSD, NetBSD, FreeBSD, DragonFlyBSD, OSX and Linux.

The archives are now available from the main site at

We would like to thank the OpenSMTPD community for their help in testing
the snapshots, reporting bugs, contributing code and packaging for other

This is a minor release with security and reliability fixes only.
You are encouraged to update as soon as possible.

The following issues, among others less critical, were discovered during
a code audit performed by Qualys Security []. This
has been a very impressive and valuable contribution to our project, and
we'd like to thank them again for this ;-)

Issues fixed in this release (since 5.7.1):

- - an oversight in the portable version of fgetln() that allows attackers
  to read and write out-of-bounds memory;

- - multiple denial-of-service vulnerabilities that allow local users to
  kill or hang OpenSMTPD;

- - a stack-based buffer overflow that allows local users to crash
  OpenSMTPD, or execute arbitrary code as the non-chrooted _smtpd user;

- - a hardlink attack (or race-conditioned symlink attack) that allows
  local users to unset the chflags() of arbitrary files;

- - a hardlink attack that allows local users to read the first line of
  arbitrary files (for example, root's hash from /etc/master.passwd);

- - a denial-of-service vulnerability that allows remote attackers to fill
  OpenSMTPD's queue or mailbox hard-disk partition;

- - an out-of-bounds memory read that allows remote attackers to crash
  OpenSMTPD, or leak information and defeat the ASLR protection;

- - a use-after-free vulnerability that allows remote attackers to crash
  OpenSMTPD, or execute arbitrary code as the non-chrooted _smtpd user;


  SHA256 (opensmtpd-5.7.2.tar.gz) =

  SHA256 (opensmtpd-5.7.2p1.tar.gz) =


Starting with version 5.7.1, releases are signed with signify(1).

You can obtain the public key from our website, check with our community
that it has not been altered on its way to your machine.

Once you are confident the key is correct, you can verify the release as
described below:

1- get the signature file corresponding to the tarball you're installing

   $ wget

2- check that the tarball matches the checksum:

   $ sha256 opensmtpd-5.7.2.tar.gz
   SHA256 (opensmtpd-5.7.2.tar.gz) =
   $ cat opensmtpd-5.7.2.sum.sig |tail -1

3- verify that the signature file was not forged:

   $ signify -V -e -p -m opensmtpd-5.7.2.sum
   Signature Verified


You are encouraged to register to our general purpose mailing-list:

The "Official" IRC channel for the project is at:
    #OpenSMTPD @

Reporting Bugs:

Please read
Security bugs should be reported directly to
Other bugs may be reported to

OpenSMTPD is brought to you by Gilles Chehade, Eric Faurot and
Sunil Nimmagadda.

- --------------------------END INCLUDED TEXT--------------------

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This security bulletin is provided as a service to AusCERT's members.  As
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NOTE: This is only the original release of the security bulletin.  It may
not be updated when updates to the original are made.  If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.

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in the Security Bulletin above.  If you have any questions or need further
information, please contact them directly.

Previous advisories and external security bulletins can be retrieved from:

Australian Computer Emergency Response Team
The University of Queensland
Qld 4072

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