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osvGoogleOSV:DLA-387-1
HistoryJan 14, 2016 - 12:00 a.m.

openssh - security update

2016-01-1400:00:00
Google
osv.dev
10

8.1 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

4.6 Medium

CVSS2

Access Vector

NETWORK

Access Complexity

HIGH

Authentication

SINGLE

Confidentiality Impact

PARTIAL

Integrity Impact

PARTIAL

Availability Impact

PARTIAL

AV:N/AC:H/Au:S/C:P/I:P/A:P

The Qualys Security team discovered two vulnerabilities in the roaming
code of the OpenSSH client (an implementation of the SSH protocol
suite).

SSH roaming enables a client, in case an SSH connection breaks
unexpectedly, to resume it at a later time, provided the server also
supports it.

The OpenSSH server doesn’t support roaming, but the OpenSSH client
supports it (even though it’s not documented) and it’s enabled by
default.

  • CVE-2016-0777
    An information leak (memory disclosure) can be exploited by a rogue
    SSH server to trick a client into leaking sensitive data from the
    client memory, including for example private keys.
  • CVE-2016-0778
    A buffer overflow (leading to file descriptor leak), can also be
    exploited by a rogue SSH server, but due to another bug in the code
    is possibly not exploitable, and only under certain conditions (not
    the default configuration), when using ProxyCommand, ForwardAgent or
    ForwardX11.

This security update completely disables the roaming code in the OpenSSH
client.

It is also possible to disable roaming by adding the (undocumented)
option UseRoaming no to the global /etc/ssh/ssh_config file, or to the
user configuration in ~/.ssh/config, or by passing -oUseRoaming=no on
the command line.

Users with passphrase-less privates keys, especially in non interactive
setups (automated jobs using ssh, scp, rsync+ssh etc.) are advised to
update their keys if they have connected to an SSH server they don’t
trust.

More details about identifying an attack and mitigations can be found in
the Qualys Security Advisory.

8.1 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

4.6 Medium

CVSS2

Access Vector

NETWORK

Access Complexity

HIGH

Authentication

SINGLE

Confidentiality Impact

PARTIAL

Integrity Impact

PARTIAL

Availability Impact

PARTIAL

AV:N/AC:H/Au:S/C:P/I:P/A:P