Security Bulletin
Summary
The Logjam Attack on TLS connections using the Diffie-Hellman (DH) key exchange protocol affects IBM Datapower Gateways.
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
All DataPower products and versions that are configured to perform SSL/TLS transactions as a client.
Remediation/Fixes
Fix is available in versions 6.0.0.16, 6.0.1.12, 7.0.0.9, 7.1.0.6, 7.2.0.1. Refer to APAR IT10061 for URLs to download the fix.
Note that the workaround/mitigation is only required in the affected versions of DataPower.
You should verify applying this fix does not cause any compatibility issues.
For DataPower customers using versions 5.x and older versions, IBM recommends upgrading to a fixed, supported version/release/platform of the product.
Workarounds and Mitigations
DataPower appliances acting as an SSL server are not vulnerable.
For appliances acting as an SSL client, and which have not been upgraded to the fixed firmware versions, disable DH ciphers in DataPower.
To disable the DH ciphers in DataPower, refer to the steps below.
- Quiesce all domains and services to stop traffic to the appliance. System quiesce and unquiesce commands can be run by navigating to Administration > Main > System Control.
- Select Objects > Crypto Configuration > Crypto Profile in the left navigation pane. For all the crypto profiles that are configured in the Configure Crypto Profile page, suffix the existing Ciphers string with a value :!DH:!kEDH and click Apply.
For example, if you have a default configuration, the updates appears as below:
Default cipher string: HIGH:MEDIUM:!aNULL:!eNULL:@STRENGTH
DH disabled cipher string: HIGH:MEDIUM:!aNULL:!eNULL:@STRENGTH:!DH:!kEDH
Note that DH must be disabled in all the crypto profiles configured in all the domains when used in an SSL client profile.
You should verify applying this configuration change does not cause any compatibility issues.
Not disabling the DH stream cipher 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 DH stream cipher and take appropriate mitigation and remediation actions.
Get Notified about Future Security Bulletins
References
Acknowledgement
Reported to IBM by The WeakDH team at https://weakdh.org
Change History
8 June 2015 Original Version Published
26 October 2015 Updated with remediation details
*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.
Internal Use Only
Awaiting a patch from OpenSSL to incorporate in a fix pack.
Was this topic helpful?
Document Information
Modified date:
15 June 2018
UID
swg21959060