Security Bulletin: Vulnerabilities in OpenSSH affect GPFS V3.5 for Windows (CVE-2016-0777, CVE-2016-0778)

Summary

An information leak flaw and buffer overflow flaw in the way the OpenSSH client roaming feature was implemented affects OpenSSH for GPFS V3.5.

Vulnerability Details

CVEID: 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 https://exchange.xforce.ibmcloud.com/vulnerabilities/109635 for the 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)

CVEID: 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 https://exchange.xforce.ibmcloud.com/vulnerabilities/109636 for the 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

OpenSSH for GPFS V3.5 for Windows

Remediation/Fixes

In GPFS V3.5.0.31 dated May 2016, IBM upgraded OpenSSH for GPFS on Windows to 7.2p2 and to use OpenSSL 1.0.2h to address these vulnerabilities. System administrators should update their systems to GPFS V3.5.0.31 by following the steps below.

1. Download the GPFS 3.5.0.31 update package dated May 2016 into any directory on your system from http://www-933.ibm.com/support/fixcentral/swg/selectFixes?parent=Cluster%2Bsoftware&product=ibm/power/IBM+General+Parallel+File+System&release=3.5.0&platform=Windows&function=all

2. Extract the contents of the ZIP archive so that the .msi file it includes is directly accessible to your system.

3. Follow the instructions in the README included in the update package in order to install the OpenSSH msi package. This updated OpenSSH 7.2.p2 msi package is built using OpenSSL 1.02h.

If GPFS multiclustering is configured on Windows nodes, upgrade all OpenSSL packages that may have been installed. The following can be done on a small group of nodes at each time (ensuring that quorum is maintained) to maintain file system availability:

a. Stop GPFS on the node
b. Install the version of OpenSSL
c. Restart GPFS on the node

Workarounds and Mitigations

You can mitigate this issue by setting the following option in the OpenSSH client’s configuration file, either global (/usr/local/etc/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.