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Security Bulletin: Vulnerability in Diffie-Hellman ciphers affects Sterling Connect:Enterprise for UNIX (CVE-2015-4000)

Security Bulletin


Summary

The Logjam Attack on TLS connections using the Diffie-Hellman (DH) key exchange protocol affects Sterling Connect:Enterprise for UNIX when using the AS2 or WebDAV protocols.

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

Sterling Connect:Enterprise for UNIX 2.5.0.0 - 2.5.0.3 iFix 7
Sterling Connect:Enterprise for UNIX 2.4.4.0 - 2.4.4.0 Build 199

Remediation/Fixes

None

Workarounds and Mitigations

To ensure that the Diffie-Hellman export ciphers are not used in the AS2 or WebDAV protocols in Sterling Connect:Enterprise for UNIX, do the following:

1. Bring up the Sterling Connect:Enterprise for UNIX Administration Tool.

2. Navigate to the Manage System / Define Configuration panel and edit each Protocol Definition name which uses HTTP or WebDAV and is secure (i.e. has a Cipher Strength other than “None”).

    - Select Cipher Strength of “Custom”
    - Select the ciphers which include “3DES” in the name
    - Click Save and go to the next protocol definition name

3. You must restart Sterling Connect:Enterprise for UNIX to pick up the changes.


You should verify applying this configuration change does not cause any compatibility issues. Not disabling the Diffie-Hellman export ciphers will expose you 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.

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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.

References

Off

Acknowledgement

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

Change History

10 June 2015: Original Version Published

*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

Review the IBM security bulletin disclaimer and definitions regarding your responsibilities for assessing potential impact of security vulnerabilities to your environment.

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Document Information

Modified date:
17 December 2019

UID

swg21959585