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Security Bulletin: Vulnerability with Diffie-Hellman ciphers may affect IBM WebSphere Application Server (CVE-2015-4000)

Security Bulletin


Summary

The LogJam Attack on Diffie-Hellman ciphers (CVE-2015-4000) may affect some configurations of IBM WebSphere Application Server Full Profile, IBM WebSphere Application Server Liberty Profile, and IBM WebSphere Application Server Hypervisor Edition. The IBM HTTP Server used by WebSphere Application Server is not affected.

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 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

The following IBM WebSphere Application Server Versions may be affected:

  • Version 8.5 and 8.5.5 Full Profile and Liberty Profile
  • Version 8
  • Version 7
  • Version 6.1

Remediation/Fixes

For IBM WebSphere Application Server and IBM WebSphere Application Server Hypervisor Edition :

You should apply the correct Interim Fix as noted below for your version of the IBM SDK Java Technology Edition. You will also need to update your java.security file to add
jdk.tls.disabledAlgorithms=SSLv3, RC4, DH keySize <768

Adding this line to the java.security file will disable features exploited by Poodle, RC4 (Bar Mitzvah), and logjam vulnerabilities.
The IBM Java SDK already has SSLv3 disabled by default and the WebSphere Application Server default configuration does not have any RC4 Ciphers. As such adding the jdk.tls.disabledAlgorithims= for SSLv3 and RC4 is redundant but is consistent with what is required for a stand alone JDK. The java.security file must be updated on the client side with the DH keySize so that is it not vulnerable to the logjam attack. The DH Keysize<768 means that the client will only accept DH keys greater than or equal to 768.

APAR IV73934 - includes the fix for CVE-2015-4000 for IBM SDK, Java Technology Edition, Versions 6, 7 and 8
APAR IV73962 - includes the fix for CVE-2015-4000 for IBM SDK, Java 2 Technology Edition Version 5

Download and apply the interim fix APARs below, for your appropriate release

For V8.5.0.0 through 8.5.5.6 Liberty Profile:

Upgrade to WebSphere Application Server Liberty Profile Fix Pack 8.5.5.1 or later then apply one of the interim fixes below:

  • Apply Interim Fix PI42781: Will upgrade you to IBM SDK, Java Technology Edition, Version 6R1 Service Refresh 8 (required) +IX90162+IV73188+IV73636+IV73934
  • Apply Interim Fix PI42775: Will upgrade you to IBM SDK, Java Technology Edition, Version 7 Service Refresh 9 (optional) +IX90162+IV73188+IV73636+IV73934
  • Apply Interim Fix PI42774: Will upgrade you to IBM SDK, Java Technology Edition, Version 7R1 Service Refresh 3 (optional) +IX90162+IV73188+IV73636+IV73934
  • Apply Interim Fix PI42733: Will upgrade you to IBM SDK, Java Technology Edition, Version 8 Service Refresh 1 (optional) +IX90162+IV73188+IV73636+IV73934
--OR--
  • Apply IBM Java SDK shipped with WebSphere Application Server Fix pack 7 (8.5.5.7) or later.

For V8.5.0.0 through 8.5.5.6 Full Profile:

Upgrade to WebSphere Application Server Full Profile Fix Pack 8.5.5.1 or later then apply one of the interim fixes below:

  • Apply Interim Fix PI42776: Will upgrade you to IBM SDK, Java Technology Edition, Version 6R1 Service Refresh 8 Fix Pack 4 (required) +IX90162 +IV73188 +IV73636 +IV73934
  • Apply Interim Fix PI42775: Will upgrade you to IBM SDK, Java Technology Edition, Version 7 Service Refresh 9 (optional) +IX90162+IV73188+IV73636+IV73934
  • Apply Interim Fix PI42774: Will upgrade you to IBM SDK, Java Technology Edition, Version 7R1 Service Refresh 3 (optional) +IX90162+IV73188+IV73636+IV73934
--OR--
  • Apply IBM Java SDK shipped with the WebSphere Application Server Fix pack 7 (8.5.5.7) or later.


For V8.0.0.0 through 8.0.0.10:

Upgrade to WebSphere Application Server Fix Pack 8.0.0.7 or later then apply the interim fix below:

  • Apply Interim Fix PI42777: Will upgrade you to IBM SDK, Java Technology Edition, Version 6R1 Service Refresh 8 Fix Pack 4 +IX90162+IV73188+IV73934
--OR--
  • Apply IBM Java SDK shipped with WebSphere Application Server Fix pack 11 (8.0.0.11) or later.

For V7.0.0.0 through 7.0.0.37:

Upgrade to WebSphere Application Server Fix Pack 7.0.0.31 or later then apply the interim fix below:

  • Apply Interim Fix PI42778: Will upgrade you to IBM SDK, Java Technology Edition, Version 6 Service Refresh 16 Fix Pack 4 +IX90162+IV73934
--OR--
  • Apply IBM Java SDK shipped with WebSphere Application Server Fix pack 39 (7.0.0.39) or later.

For V6.1.0.0 through 6.1.0.47:

Upgrade to WebSphere Application Server Fix Pack 6.1.0.47

  • Then apply Interim Fix PI42779: Will upgrade you to IBM SDK, Java 2 Technology Edition, Version 5.0 Service Refresh 16 Fix Pack 11 (which includes IV73962)


NOTE: As the length of the server key size are increased, the amount of CPU required for full TLS/SSL handshake can significantly increase. Please carefully test and assess the impact to your CPU requirements to ensure sufficient CPU resources, otherwise the system availability may be impacted.

After you have applied the correct Interim fix for your version of the IBM SDK Java Technology Edition. You will also need to update your java.security file to add

jdk.tls.disabledAlgorithms=SSLv3, RC4, DH keySize <768
Adding this line to the java.security file will disable features exploited by Poodle, RC4 (Bar Mitzvah), and logjam vulnerabilities.
The IBM Java SDK already has SSLv3 disabled by default and the WebSphere Application Server default configuration does not have any RC4 Ciphers. As such adding the jdk.tls.disabledAlgorithims= for SSLv3 and RC4 is redundant but is consistent with what is required for a stand alone JDK. The java.security file must be updated on the client side with the DH keySize so that is it not vulnerable to the logjam attack. The DH Keysize<768 means that the client will only accept DH keys greater than or equal to 768.


For IBM WebSphere Application Server for i5/OS operating systems:


The IBM Developer Kit for Java is prerequisite software for WebSphere Application Server for IBM i. Please refer to Java on IBM i for updates on when these fixes will be available.

Workarounds and Mitigations

The Logjam attack which affects TLS connections using the Diffie-Hellman (DH) key exchange protocol may affect some configurations in WebSphere Application Server.

WebSphere Application Server has DH and DHE ciphers included in the "STRONG" or "HIGH", "MEDIUM" and "LOW" cipher lists. They also could be present if you have a "CUSTOM" list of ciphers. You will need to remove any of the ciphers that begin with SSL_* or TLS_* that also have DH or DHE in the Name from your WebSphere Application Server SSL configuration. This does NOT include ciphers that have ECDH or ECDHE in the Name, these are elliptic curve Diffie-Hellman ciphers and they are not affected.

For Full profile:

  • You can view the administrative console page to change the settings, click Security > SSL certificate and key management. Under Configuration settings, click Manage endpoint security configurations > {Inbound | Outbound} > ssl_configuration. Under Related items, click SSL configurations > . Click on {SSL_configuration_name }. Under Additional Properties, click Quality of protection (QoP) settings.
  • For more information on the Quality of Protection settings refer to the Knowledge Center: http://www-01.ibm.com/support/knowledgecenter/SSAW57_8.5.5/com.ibm.websphere.nd.doc/ae/usec_sslqualprotect.html?lang=en

OR

For Liberty profile:

Outbound connections from WebSphere Application Server are impacted but inbound connections are not.

You should verify applying this configuration change does not cause any compatibility issues. Not disabling the DH or DHE stream ciphers will expose yourself to the Logjam 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.

Get Notified about Future Security Bulletins

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

Related information

Acknowledgement

Reported to IBM by The WeakDH team at https://weakdh.org

Change History

01 June 2015: original document published
10 June 2015: updated mitigation section
24 June 2015: added remediation section
29 June 2015: removed IV73188 from Java 6 for WAS version 7
30 June 2015: added more wording on java.security file updates
09 July 2015: clarified wording on java.security file updates

*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.


Cross reference information
Segment Product Component Platform Version Edition
Application Servers IBM HTTP Server
Application Servers WebSphere Application Server Hypervisor Edition
Application Servers WebSphere Application Server Liberty Core

Document information

More support for: WebSphere Application Server
Security

Software version: 6.1, 7.0, 8.0, 8.5, 8.5.5

Operating system(s): AIX, HP-UX, IBM i, Linux, Solaris, Windows, z/OS

Software edition: Base, Developer, Enterprise, Liberty, Network Deployment

Reference #: 1957980

Modified date: 08 July 2015