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Category:   Application (VPN)  >   OpenSSL Vendors:   OpenSSL.org
(Red Hat Issues Fix) OpenSSL TLS Diffie-Hellman Export Cipher Downgrade Attack Lets Remote Users Decrypt Connections
SecurityTracker Alert ID:  1032506
SecurityTracker URL:  http://securitytracker.com/id/1032506
CVE Reference:   CVE-2015-4000   (Links to External Site)
Date:  Jun 4 2015
Impact:   Modification of authentication information
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  

Description:   A vulnerability was reported in OpenSSL. A remote user may be able to decrypt TLS connections in certain situations.

A remote user that can conduct a man-in-the-middle attack can cause the target system to downgrade the Diffie-Hellman algorithm to 512-bit export-grade cryptography. The remote user may then be able to decrypt the connection.

This vulnerability resides in the TLS protocol and not in the specific TLS implementation, but the vulnerability is exposed because the target system supports export-grade ciphers.

This attack is known as the "Logjam" attack.

The original advisory is available at:

https://weakdh.org/imperfect-forward-secrecy.pdf

David Adrian, Karthikeyan Bhargavan, Zakir Durumeric, Pierrick Gaudry, Matthew Green, J. Alex Halderman, Nadia Heninger, Drew Springall, Emmanuel Thome, Luke Valenta, Benjamin VanderSloot, Eric Wustrow, Santiago Zanella-Beguelin, and Paul Zimmermann reported this vulnerability.

Impact:   A remote user that can conduct a man-in-the-middle attack can cause the target system to use weak cryptography that can be decrypted.
Solution:   Red Hat has issued a fix.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2015-1072.html

Vendor URL:  www.openssl.org/news/secadv_20150611.txt (Links to External Site)
Cause:   Authentication error
Underlying OS:  Linux (Red Hat Enterprise)
Underlying OS Comments:  6, 7

Message History:   This archive entry is a follow-up to the message listed below.
Jun 3 2015 OpenSSL TLS Diffie-Hellman Export Cipher Downgrade Attack Lets Remote Users Decrypt Connections



 Source Message Contents

Subject:  [RHSA-2015:1072-01] Moderate: openssl security update

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Hash: SHA1

=====================================================================
                   Red Hat Security Advisory

Synopsis:          Moderate: openssl security update
Advisory ID:       RHSA-2015:1072-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2015-1072.html
Issue date:        2015-06-04
CVE Names:         CVE-2015-4000 
=====================================================================

1. Summary:

Updated openssl packages that fix one security issue are now available for
Red Hat Enterprise Linux 6 and 7.

Red Hat Product Security has rated this update as having Moderate security
impact. A Common Vulnerability Scoring System (CVSS) base score, which
gives a detailed severity rating, is available from the CVE link in the
References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux Client (v. 7) - x86_64
Red Hat Enterprise Linux Client Optional (v. 7) - x86_64
Red Hat Enterprise Linux ComputeNode (v. 7) - x86_64
Red Hat Enterprise Linux ComputeNode Optional (v. 7) - x86_64
Red Hat Enterprise Linux Desktop (v. 6) - i386, x86_64
Red Hat Enterprise Linux Desktop Optional (v. 6) - i386, x86_64
Red Hat Enterprise Linux HPC Node (v. 6) - x86_64
Red Hat Enterprise Linux HPC Node Optional (v. 6) - x86_64
Red Hat Enterprise Linux Server (v. 6) - i386, ppc64, s390x, x86_64
Red Hat Enterprise Linux Server (v. 7) - ppc64, ppc64le, s390x, x86_64
Red Hat Enterprise Linux Server Optional (v. 6) - i386, ppc64, s390x, x86_64
Red Hat Enterprise Linux Server Optional (v. 7) - ppc64, ppc64le, s390x, x86_64
Red Hat Enterprise Linux Workstation (v. 6) - i386, x86_64
Red Hat Enterprise Linux Workstation (v. 7) - x86_64
Red Hat Enterprise Linux Workstation Optional (v. 6) - i386, x86_64
Red Hat Enterprise Linux Workstation Optional (v. 7) - x86_64

3. Description:

OpenSSL is a toolkit that implements the Secure Sockets Layer (SSL v2/v3)
and Transport Layer Security (TLS v1) protocols, as well as a
full-strength, general purpose cryptography library.

A flaw was found in the way the TLS protocol composes the Diffie-Hellman
(DH) key exchange. A man-in-the-middle attacker could use this flaw to
force the use of weak 512 bit export-grade keys during the key exchange,
allowing them do decrypt all traffic. (CVE-2015-4000)

Note: This update forces the TLS/SSL client implementation in OpenSSL to
reject DH key sizes below 768 bits, which prevents sessions to be
downgraded to export-grade keys. Future updates may raise this limit to
1024 bits.

All openssl users are advised to upgrade to these updated packages, which
contain a backported patch to correct this issue. For the update to take
effect, all services linked to the OpenSSL library must be restarted, or
the system rebooted.

4. Solution:

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

5. Bugs fixed (https://bugzilla.redhat.com/):

1223211 - CVE-2015-4000 LOGJAM: TLS connections which support export grade DHE key-exchange are vulnerable to MITM attacks

6. Package List:

Red Hat Enterprise Linux Desktop (v. 6):

Source:
openssl-1.0.1e-30.el6_6.9.src.rpm

i386:
openssl-1.0.1e-30.el6_6.9.i686.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm

x86_64:
openssl-1.0.1e-30.el6_6.9.i686.rpm
openssl-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.x86_64.rpm

Red Hat Enterprise Linux Desktop Optional (v. 6):

i386:
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-devel-1.0.1e-30.el6_6.9.i686.rpm
openssl-perl-1.0.1e-30.el6_6.9.i686.rpm
openssl-static-1.0.1e-30.el6_6.9.i686.rpm

x86_64:
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-devel-1.0.1e-30.el6_6.9.i686.rpm
openssl-devel-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-perl-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-static-1.0.1e-30.el6_6.9.x86_64.rpm

Red Hat Enterprise Linux HPC Node (v. 6):

Source:
openssl-1.0.1e-30.el6_6.9.src.rpm

x86_64:
openssl-1.0.1e-30.el6_6.9.i686.rpm
openssl-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.x86_64.rpm

Red Hat Enterprise Linux HPC Node Optional (v. 6):

x86_64:
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-devel-1.0.1e-30.el6_6.9.i686.rpm
openssl-devel-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-perl-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-static-1.0.1e-30.el6_6.9.x86_64.rpm

Red Hat Enterprise Linux Server (v. 6):

Source:
openssl-1.0.1e-30.el6_6.9.src.rpm

i386:
openssl-1.0.1e-30.el6_6.9.i686.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-devel-1.0.1e-30.el6_6.9.i686.rpm

ppc64:
openssl-1.0.1e-30.el6_6.9.ppc.rpm
openssl-1.0.1e-30.el6_6.9.ppc64.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.ppc.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.ppc64.rpm
openssl-devel-1.0.1e-30.el6_6.9.ppc.rpm
openssl-devel-1.0.1e-30.el6_6.9.ppc64.rpm

s390x:
openssl-1.0.1e-30.el6_6.9.s390.rpm
openssl-1.0.1e-30.el6_6.9.s390x.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.s390.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.s390x.rpm
openssl-devel-1.0.1e-30.el6_6.9.s390.rpm
openssl-devel-1.0.1e-30.el6_6.9.s390x.rpm

x86_64:
openssl-1.0.1e-30.el6_6.9.i686.rpm
openssl-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-devel-1.0.1e-30.el6_6.9.i686.rpm
openssl-devel-1.0.1e-30.el6_6.9.x86_64.rpm

Red Hat Enterprise Linux Server Optional (v. 6):

i386:
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-perl-1.0.1e-30.el6_6.9.i686.rpm
openssl-static-1.0.1e-30.el6_6.9.i686.rpm

ppc64:
openssl-debuginfo-1.0.1e-30.el6_6.9.ppc64.rpm
openssl-perl-1.0.1e-30.el6_6.9.ppc64.rpm
openssl-static-1.0.1e-30.el6_6.9.ppc64.rpm

s390x:
openssl-debuginfo-1.0.1e-30.el6_6.9.s390x.rpm
openssl-perl-1.0.1e-30.el6_6.9.s390x.rpm
openssl-static-1.0.1e-30.el6_6.9.s390x.rpm

x86_64:
openssl-debuginfo-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-perl-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-static-1.0.1e-30.el6_6.9.x86_64.rpm

Red Hat Enterprise Linux Workstation (v. 6):

Source:
openssl-1.0.1e-30.el6_6.9.src.rpm

i386:
openssl-1.0.1e-30.el6_6.9.i686.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-devel-1.0.1e-30.el6_6.9.i686.rpm

x86_64:
openssl-1.0.1e-30.el6_6.9.i686.rpm
openssl-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-debuginfo-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-devel-1.0.1e-30.el6_6.9.i686.rpm
openssl-devel-1.0.1e-30.el6_6.9.x86_64.rpm

Red Hat Enterprise Linux Workstation Optional (v. 6):

i386:
openssl-debuginfo-1.0.1e-30.el6_6.9.i686.rpm
openssl-perl-1.0.1e-30.el6_6.9.i686.rpm
openssl-static-1.0.1e-30.el6_6.9.i686.rpm

x86_64:
openssl-debuginfo-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-perl-1.0.1e-30.el6_6.9.x86_64.rpm
openssl-static-1.0.1e-30.el6_6.9.x86_64.rpm

Red Hat Enterprise Linux Client (v. 7):

Source:
openssl-1.0.1e-42.el7_1.6.src.rpm

x86_64:
openssl-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.i686.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-libs-1.0.1e-42.el7_1.6.i686.rpm
openssl-libs-1.0.1e-42.el7_1.6.x86_64.rpm

Red Hat Enterprise Linux Client Optional (v. 7):

x86_64:
openssl-debuginfo-1.0.1e-42.el7_1.6.i686.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-devel-1.0.1e-42.el7_1.6.i686.rpm
openssl-devel-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-perl-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-static-1.0.1e-42.el7_1.6.i686.rpm
openssl-static-1.0.1e-42.el7_1.6.x86_64.rpm

Red Hat Enterprise Linux ComputeNode (v. 7):

Source:
openssl-1.0.1e-42.el7_1.6.src.rpm

x86_64:
openssl-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.i686.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-libs-1.0.1e-42.el7_1.6.i686.rpm
openssl-libs-1.0.1e-42.el7_1.6.x86_64.rpm

Red Hat Enterprise Linux ComputeNode Optional (v. 7):

x86_64:
openssl-debuginfo-1.0.1e-42.el7_1.6.i686.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-devel-1.0.1e-42.el7_1.6.i686.rpm
openssl-devel-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-perl-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-static-1.0.1e-42.el7_1.6.i686.rpm
openssl-static-1.0.1e-42.el7_1.6.x86_64.rpm

Red Hat Enterprise Linux Server (v. 7):

Source:
openssl-1.0.1e-42.el7_1.6.src.rpm

ppc64:
openssl-1.0.1e-42.el7_1.6.ppc64.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.ppc.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.ppc64.rpm
openssl-devel-1.0.1e-42.el7_1.6.ppc.rpm
openssl-devel-1.0.1e-42.el7_1.6.ppc64.rpm
openssl-libs-1.0.1e-42.el7_1.6.ppc.rpm
openssl-libs-1.0.1e-42.el7_1.6.ppc64.rpm

s390x:
openssl-1.0.1e-42.el7_1.6.s390x.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.s390.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.s390x.rpm
openssl-devel-1.0.1e-42.el7_1.6.s390.rpm
openssl-devel-1.0.1e-42.el7_1.6.s390x.rpm
openssl-libs-1.0.1e-42.el7_1.6.s390.rpm
openssl-libs-1.0.1e-42.el7_1.6.s390x.rpm

x86_64:
openssl-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.i686.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-devel-1.0.1e-42.el7_1.6.i686.rpm
openssl-devel-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-libs-1.0.1e-42.el7_1.6.i686.rpm
openssl-libs-1.0.1e-42.el7_1.6.x86_64.rpm

Red Hat Enterprise Linux Server (v. 7):

Source:
openssl-1.0.1e-42.ael7b_1.6.src.rpm

ppc64le:
openssl-1.0.1e-42.ael7b_1.6.ppc64le.rpm
openssl-debuginfo-1.0.1e-42.ael7b_1.6.ppc64le.rpm
openssl-devel-1.0.1e-42.ael7b_1.6.ppc64le.rpm
openssl-libs-1.0.1e-42.ael7b_1.6.ppc64le.rpm

Red Hat Enterprise Linux Server Optional (v. 7):

ppc64:
openssl-debuginfo-1.0.1e-42.el7_1.6.ppc.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.ppc64.rpm
openssl-perl-1.0.1e-42.el7_1.6.ppc64.rpm
openssl-static-1.0.1e-42.el7_1.6.ppc.rpm
openssl-static-1.0.1e-42.el7_1.6.ppc64.rpm

s390x:
openssl-debuginfo-1.0.1e-42.el7_1.6.s390.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.s390x.rpm
openssl-perl-1.0.1e-42.el7_1.6.s390x.rpm
openssl-static-1.0.1e-42.el7_1.6.s390.rpm
openssl-static-1.0.1e-42.el7_1.6.s390x.rpm

x86_64:
openssl-debuginfo-1.0.1e-42.el7_1.6.i686.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-perl-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-static-1.0.1e-42.el7_1.6.i686.rpm
openssl-static-1.0.1e-42.el7_1.6.x86_64.rpm

Red Hat Enterprise Linux Server Optional (v. 7):

ppc64le:
openssl-debuginfo-1.0.1e-42.ael7b_1.6.ppc64le.rpm
openssl-perl-1.0.1e-42.ael7b_1.6.ppc64le.rpm
openssl-static-1.0.1e-42.ael7b_1.6.ppc64le.rpm

Red Hat Enterprise Linux Workstation (v. 7):

Source:
openssl-1.0.1e-42.el7_1.6.src.rpm

x86_64:
openssl-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.i686.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-devel-1.0.1e-42.el7_1.6.i686.rpm
openssl-devel-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-libs-1.0.1e-42.el7_1.6.i686.rpm
openssl-libs-1.0.1e-42.el7_1.6.x86_64.rpm

Red Hat Enterprise Linux Workstation Optional (v. 7):

x86_64:
openssl-debuginfo-1.0.1e-42.el7_1.6.i686.rpm
openssl-debuginfo-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-perl-1.0.1e-42.el7_1.6.x86_64.rpm
openssl-static-1.0.1e-42.el7_1.6.i686.rpm
openssl-static-1.0.1e-42.el7_1.6.x86_64.rpm

These packages are GPG signed by Red Hat for security.  Our key and
details on how to verify the signature are available from
https://access.redhat.com/security/team/key/

7. References:

https://access.redhat.com/security/cve/CVE-2015-4000
https://access.redhat.com/security/updates/classification/#moderate
https://access.redhat.com/articles/1456263
https://www.openssl.org/blog/blog/2015/05/20/logjam-freak-upcoming-changes/

8. Contact:

The Red Hat security contact is <secalert@redhat.com>. More contact
details at https://access.redhat.com/security/team/contact/

Copyright 2015 Red Hat, Inc.
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