03 June 2015
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== 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 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- 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 - --------------------------BEGIN INCLUDED TEXT-------------------- 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 Subscribe to My Notifications to be notified of important product support 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. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. 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