Security Bulletin
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.
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References
Change History
7 June 2016: Updated Remediation/Fixes
12 Feb 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
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:
25 June 2021
UID
isg3T1023321