Security Bulletin: Vulnerabilities in OpenSSH affect IBM Flex System Chassis Management Module (CVE-2016-0777, CVE-2016-0778)

Vulnerability Details

Summary

An information leak flaw and buffer overflow flaw in the way the OpenSSH client roaming feature was implemented affects IBM Flex System Chassis Management Module (CMM).

Vulnerability Details:

CVE-ID: CVE-2016-0777

Description: OpenSSH could allow a remote attacker to obtain sensitive information, caused by a client information leak from using the roaming connection feature. By persuading a victim to connect to a malicious server, an attacker could exploit this vulnerability to retrieve private cryptographic keys or other sensitive information.

CVSS Base Score: 6.5
CVSS Temporal Score: See http://exchange.xforce.ibmcloud.com/vulnerabilities/109635 for current score
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N)

CVE-ID: CVE-2016-0778

Description: OpenSSH is vulnerable to a heap-based buffer overflow, caused by improper bounds checking by the packet_write_wait() and ssh_packet_write_wait() API functions when two non-default options: a ProxyCommand and either ForwardAgent or ForwardX11are used. By persuading a victim to connect to a malicious server, a remote attacker could overflow a buffer and execute arbitrary code on the system or cause the application to crash.

CVSS Base Score: 5
CVSS Temporal Score: See http://exchange.xforce.ibmcloud.com/vulnerabilities/109636 for current score
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:L)

Affected Products and Versions

Remediation/Fixes:

Firmware fix versions are available on Fix Central:
http://www.ibm.com/support/fixcentral/.

You should verify applying this fix does not cause any compatibility issues.

After applying fix, IBM recommends that you regenerate your SSH keys as a precaution.

Workarounds and Mitigations:

You can mitigate this issue by setting the following option in the OpenSSH client's configuration file, either global (/etc/ssh/ssh_config) or user specific (~/.ssh/config):
UseRoaming no

Be sure you place the above in the Host * section of the configuration file to use this setting for all SSH servers the client connects to.

You can also set the option through the command line argument when connecting to an SSH server:
-o 'UseRoaming no'

After applying mitigation, IBM recommends that you regenerate your SSH keys as a precaution.

References:

• Complete CVSS v3 Guide
• On-line Calculator v3

Related Information:
IBM Secure Engineering Web Portal
IBM Product Security Incident Response Blog

Acknowledgement

None.

Change History
06 April 2016: 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

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.