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MEDIUM

OpenSSH: Client Information leak due to use of roaming connection feature

Published Jan 14, 2016

Description

The resend_bytes function in roaming_common.c in the client in OpenSSH 5.x, 6.x, and 7.x before 7.1p2 allows remote servers to obtain sensitive information from process memory by requesting transmission of an entire buffer, as demonstrated by reading a private key.

Affected products

Remediation

Red Hat 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

Red Hat 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.

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References (40)

Change history (0)

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Sources
CVE.org / MITRE
Status PUBLISHED
Assigner redhat
Published Jan 14, 2016
Updated May 29, 2026
Reserved Dec 16, 2015
CISA Vulnrichment
Updated May 29, 2026
NVD
Status Modified
Modified Jun 17, 2026
Red Hat
Severity Moderate
Public date Jan 14, 2016