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AUSCERT External Security Bulletin Redistribution
ESB-2015.1445
Security Bulletin: Logjam vulnerability in TLS affects IBM
CICS Transaction Gateway (CVE-2015-4000)
3 June 2015
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AusCERT Security Bulletin Summary
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Product: IBM CICS Transaction Gateway
Publisher: IBM
Operating System: AIX
HP-UX
Linux variants
Solaris
Windows
Impact/Access: Access Privileged Data -- Remote/Unauthenticated
Provide Misleading Information -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2015-4000
Reference: ESB-2015.1443
ESB-2015.1432
ESB-2015.1425
Original Bulletin:
http://www-01.ibm.com/support/docview.wss?uid=swg21958030
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Security Bulletin: Logjam vulnerability in TLS affects IBM CICS Transaction
Gateway (CVE-2015-4000)
Security Bulletin
Document information
More support for:
CICS Transaction Gateway
Security
Software version:
7.2, 8.0, 8.1, 9.0, 9.1
Operating system(s):
AIX, HP-UX, Linux, Solaris, Windows
Software edition:
All
Reference #:
1958030
Modified date:
2015-06-02
Summary
The TLS protocol could allow a remote attacker to obtain sensitive
information, caused by the failure to properly convey a DHE_EXPORT ciphersuite
choice. An attacker could exploit this vulnerability using man-in-the-middle
techniques to force a downgrade to 512-bit export-grade cipher. Successful
exploitation could allow an attacker to recover the session key as well as
modify the contents of the traffic.
This vulnerability is commonly referred to as "Logjam".
Vulnerability Details
CVE ID: CVE-2015-4000
Description : The TLS protocol 1.2 and earlier, when a DHE_EXPORT ciphersuite
is enabled on a server but not on a client, does not properly convey a
DHE_EXPORT choice, which allows man-in-the-middle attackers to conduct
cipher-downgrade attacks by rewriting a ClientHello with DHE replaced by
DHE_EXPORT and then rewriting a ServerHello with DHE_EXPORT replaced by DHE,
aka the "Logjam" issue.
CVSS Base Score: 4.3
CVSS Temporal Score: See
https://exchange.xforce.ibmcloud.com/vulnerabilities/103294
CVSS Environmental Score*: Undefined
CVSS Vector: (AV:N/AC:M/Au:N/C:P/I:N/A:N)
Affected Products and Versions
CICS Transaction Gateway for Multiplatforms v7.2, v8.0, v8.1, v9.0 and v9.1.
Inclusion in this list does not imply that all the products are supported. See
the IBM Support Lifecycle page for product end of support dates
Workarounds and Mitigations
The use of DH or DHE Ciphers by CICS Transaction Gateway can be prevented by
configuring CICS TG to only accept more secure cipher suites, This can be done
by listing the acceptable cipher suites using the ciphersuites parameter in
the ctg.ini file, or by adding the acceptable cipher suites to the "Use only
these ciphers" suites in the "SSL settings" section of the CICS TG
configuration tool.
See the CICS TG for Multiplatforms Knowledge Center for more details.
Get Notified about Future Security Bulletins
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alerts like this.
Important note
IBM strongly suggests that all System z customers be subscribed to the System
z Security Portal to receive the latest critical System z security and
integrity service. If you are not subscribed, see the instructions on the
System z Security web site. Security and integrity APARs and associated fixes
will be posted to this portal. IBM suggests reviewing the CVSS scores and
applying all security or integrity fixes as soon as possible to minimize any
potential risk.
References
Complete CVSS Guide
On-line Calculator V2
Related information
IBM Secure Engineering Web Portal
IBM Product Security Incident Response Blog
*The CVSS Environment Score is customer environment specific and will
ultimately impact the Overall CVSS Score. Customers can evaluate the impact of
this vulnerability in their environments by accessing the links in the
Reference section of this Security Bulletin.
Disclaimer
According to the Forum of Incident Response and Security Teams (FIRST), the
Common Vulnerability Scoring System (CVSS) is an "industry open standard
designed to convey vulnerability severity and help to determine urgency and
priority of response." IBM PROVIDES THE CVSS SCORES "AS IS" WITHOUT WARRANTY
OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT
OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY.
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