Security Bulletin
Summary
By manipulating sequence numbers during SSH connection setup, a MITM attacker can delete negotiation messages without causing a MAC failure. To mitigate this vulnerability, IBM MQ Appliance has removed the chacha20-poly1305 cipher and all etm HMACs from the default set of algorithms offered,
Vulnerability Details
DESCRIPTION: OpenSSH is vulnerable to a machine-in-the-middle attack, caused by a flaw in the extension negotiation process in the SSH transport protocol when used with certain OpenSSH extensions. A remote attacker could exploit this vulnerability to launch a machine-in-the-middle attack and strip an arbitrary number of messages after the initial key exchange, breaking SSH extension negotiation and downgrading the client connection security.
CVSS Base score: 5.9
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/275282 for the current score.
CVSS Vector: (CVSS:3.0/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| IBM MQ Appliance | 9.3 LTS |
| IBM MQ Appliance | 9.3 CD |
Remediation/Fixes
This vulnerability is addressed under APAR IT46266
IBM MQ Appliance version 9.3 LTS
Workarounds and Mitigations
The fix removes the Chacha20-poly1305 cipher and the etm HMAC algorithms from the default set, which avoids the vulnerability. Customers may perform this same mitigation on earlier firmware versions, and should also remove these algorithms from any custom SSH configuration already deployed.
If the affected cipher and or HMACs are required for interoperability, they can be listed at the end of the cipher and MAC lists, so that they will only be used if no stronger algorithms are supported by client and server.
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References
Acknowledgement
Change History
dd mmm - Initial publication
*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. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.
Document Location
Worldwide
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Document Information
Modified date:
26 June 2024
UID
ibm17157389