CVE-2016-0777

Impact:
Moderate
Public Date:
2016-01-14
CWE:
CWE-682
Bugzilla:
1298032: CVE-2016-0777 OpenSSH: Client Information leak due to use of roaming connection feature
An information leak flaw was found in the way the OpenSSH client roaming feature was implemented. A malicious server could potentially use this flaw to leak portions of memory (possibly including private SSH keys) of a successfully authenticated OpenSSH client.

Find out more about CVE-2016-0777 from the MITRE CVE dictionary dictionary and NIST NVD.

Statement

This issue does not affect the version OpenSSH as shipped with Red Hat Enterprise Linux 4, 5 and 6. This issue affects the version of OpenSSH as shipped with Red Hat Enterprise Linux 7 in a non-default configuration. For more information please refer to https://access.redhat.com/articles/2123781

CVSS v2 metrics

Base Score 4.3
Base Metrics AV:N/AC:M/Au:N/C:P/I:N/A:N
Access Vector Network
Access Complexity Medium
Authentication None
Confidentiality Impact Partial
Integrity Impact None
Availability Impact None

Find out more about Red Hat support for the Common Vulnerability Scoring System (CVSS).

Red Hat Security Errata

Platform Errata Release Date
Red Hat Enterprise Linux 7 (openssh) RHSA-2016:0043 2016-01-14

Affected Packages State

Platform Package State
Red Hat Enterprise Linux 6 openssh Not affected
Red Hat Enterprise Linux 5 openssh Not affected
Red Hat Enterprise Linux 4 openssh Not affected

Acknowledgements

Red Hat would like to thank Qualys for reporting this issue.

Mitigation

1. The vulnerable roaming code can be permanently disabled by adding the undocumented option "UseRoaming no" to the system-wide configuration file (usually /etc/ssh/ssh_config), or per-user configuration file (~/.ssh/config), or command-line (-o "UseRoaming no"). 2. If an OpenSSH client is disconnected from an SSH server that offers roaming, it prints "[connection suspended, press return to resume]" on stderr, and waits for '\\n' or '\\r' on stdin (and not on the controlling terminal) before it reconnects to the server; advanced users may become suspicious and press Control-C or Control-Z instead, thus avoiding the information leak. However, SSH commands that use the local stdin to transfer data to the remote server are bound to trigger this reconnection automatically (upon reading a '\\n' or '\\r' from stdin). Moreover, these non-interactive SSH commands (for example, backup scripts and cron jobs) commonly employ public-key authentication and are therefore perfect targets for this information leak.

External References

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