Security Bulletin: Vulnerability in Diffie-Hellman ciphers affects IBM B2B Advanced Communications (CVE-2015-4000)

Summary

The Logjam Attack on TLS connections using the Diffie-Hellman (DH) key exchange protocol affects IBM B2B Advanced Communications.

Vulnerability Details

CVEID: CVE-2015-4000**

DESCRIPTION:** 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:
CVSS Base Score: 4.3
CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/103294 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 Multi-Enterprise Integration Gateway 1.0 - 1.0.0.1
IBM B2B Advanced Communications 1.0.0.2 - 1.0.0.3

Remediation/Fixes

The recommended solution is to upgrade to the current release as soon as practical. Please see below for information about the fixes available.

Workarounds and Mitigations

If you are not applying the fix, follow these steps to mitigate vulnerability:

To mitigate the risk exposed by the Logjam vulnerability, update the java.security parameter in the IBM SDK Java™ Technology Edition Version 7 security property file for each of your B2B Advanced Communication installations. The following instructions assume you have rights to access and edit the property file.

Procedure: Perform the following steps for each B2B Advanced Communication installation:

1. Open the security property file <installation_root>/java/jre/lib/security/java.security in a text editor

2. Find the following property:

jdk.tls.disabledAlgorithms
3) Add the following algorithms to be disabled to the property:

DH, DHE
For example, if the property currently appears as follows:

jdk.tls.disabledAlgorithms=SSLv3, RC4
After adding the Diffie-Hellman algorithms to be disabled, it should read:

jdk.tls.disabledAlgorithms=SSLv3, RC4, DH, DHE

4. Save and close the property file.

5. For the changes to take effect, stop and then start all members.

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.