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Security Bulletin: Vulnerability in Diffie-Hellman ciphers affects IBM Rational ClearCase (CVE-2015-4000)

Security Bulletin


The Logjam Attack on TLS connections using the Diffie-Hellman (DH) key exchange protocol affects IBM Rational ClearCase.

Vulnerability Details

CVEID: CVE-2015-4000
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".
CVSS Base Score: 4.3
CVSS Temporal Score: See for the current score
CVSS Environmental Score*: Undefined
CVSS Vector: (AV:N/AC:M/Au:N/C:P/I:N/A:N)

Affected Products and Versions

IBM Rational ClearCase, versions 7.1.0.x, 7.1.1.x, 7.1.2.x, 8.0.0.x, 8.0.1.x, in the following components:

  • Base CC/CQ V2 (Perl trigger-based) integration, when configured to use SSL to communicate with a ClearQuest Web server (all platforms)
  • CMI and OSLC integrations, including UCM/ClearQuest integration via OSLC (UNIX/Linux platforms), when configured to use SSL. (Windows CMI/OSLC clients are not affected.)
  • ClearCase remote client: CCRC/CTE GUI, rcleartool, and CMAPI clients, when using SSL to access a CCRC WAN Server/CM Server
  • Customer defined uses of SSL from ratlperl scripts


Install a fix pack. The fix pack includes OpenSSL version 1.0.1p and a newer Java™ Virtual Machine.

Affected Versions
Applying the fix
8.0.1 through
Install Rational ClearCase Fix Pack 9 ( for 8.0.1
8.0 through
Install Rational ClearCase Fix Pack 16 ( for 8.0
7.1.2 through
7.1.1.x (all fix packs)
7.1.0.x (all fix packs)
Customers on extended support contracts should install Rational ClearCase Fix Pack 19 ( for 7.1.2

CMI and OSLC change management integrations (UNIX/Linux platforms):
      The solution is to update to the fix pack listed above.
      Apply the fix pack to systems that use the CMI- and OSLC-based integrations. This may include CCRC WAN servers that execute the integrations on behalf of WAN clients.
Base CC/CQ Perl trigger-based (V2) integration
      The solution is to update to the fix pack listed above. Apply the fix pack to systems that run the Perl trigger-based (V2) integration, and those that run your ratlperl scripts that use OpenSSL.
Customer defined uses of SSL from ratlperl scripts
      The solution is to update to the fix pack listed above. Apply the fix pack and test fix to systems that run your ratlperl scripts that use OpenSSL.

      Alternatively, you may disable the use of the ephemeral DH key ciphers (EDH, DHE) when you use IO::Socket::SSL. The SSL_cipher_list setting configures permissible ciphers for use by OpenSSL. You can view the documentation with:
      ratlperl -e "use Pod::Perldoc; Pod::Perldoc->run();" IO::Socket::SSL

      You can view the Base CC/CQ Perl trigger-based (V2) integration for an example, in the script module <ccase-home-dir>/lib/CQCC/ See the InitAgent method that disables RC4 in this way.

ClearCase remote client: CCRC/CTE GUI, rcleartool, CMAPI clients

      The solution is to update to the fix pack listed above. Apply the fix pack to systems that run CCRC/CTE GUI, rcleartool, or CMAPI clients, such as web view and automatic view developer desktops.


      • If you use CCRC as an extension offering installed into an Eclipse shell (one not provided as part of a ClearCase release), or you use rcleartool or CMAPI using a Java™ Virtual Machine not supplied by IBM as part of Rational ClearCase, you should update the Java™ Virtual Machine you use to include a fix for the above issues (enforcing minimum key length for temporary keys used in Diffie-Hellman key exchange). Contact the supplier of your Java™ Virtual Machine.

You should verify applying this configuration change does not cause any compatibility issues. If you change the default setting after applying the fix, you will expose yourself to the attack described above. IBM recommends that you review your entire environment to identify other areas where you have enabled the Diffie-Hellman key-exchange protocol used in TLS and take appropriate mitigation and remediation actions.

For 7.0.x and earlier releases, IBM recommends upgrading to a fixed, supported version/release/platform of the product.

Workarounds and Mitigations


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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.




Reported to IBM by The WeakDH team at

Change History

*3 August 2015: Original copy published
* 16 September 2015: revised to refer to new fix pack

*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.


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.

Internal Use Only

The fixes are on the test fix portal, included in the following TestFixes: test fix 1 test fix 1 test fix 1

they can be installed using Installation Manager.

For 2015C, we will revise the instructions to apply a fix pack instead:

Apply a fix pack for your appropriate release of ClearCase.

For 7.1.0.x and 7.1.1.x customers that have support extensions with security included: the security fixes are not available on 7.1.1.x, the solution is to upgrade to 7.1.2.x. All security-supported 7.1.x customers are OK with this except Lloyds, who have not answered our repeated questions trying to get them to either agree or disagree with no security fixes on 7.1.1.x.

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Document Information

Modified date:
10 July 2018