Debian DSA-3446-1 : openssh - security update

Medium Nessus Plugin ID 87934

Synopsis

The remote Debian host is missing a security-related update.

Description

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 private 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 will be
available in the Qualys Security Advisory.

Solution

Upgrade the openssh packages.

For the oldstable distribution (wheezy), these problems have been
fixed in version 1:6.0p1-4+deb7u3.

For the stable distribution (jessie), these problems have been fixed
in version 1:6.7p1-5+deb8u1.

See Also

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=810984

https://security-tracker.debian.org/tracker/CVE-2016-0777

https://security-tracker.debian.org/tracker/CVE-2016-0778

https://packages.debian.org/source/wheezy/openssh

https://packages.debian.org/source/jessie/openssh

https://www.debian.org/security/2016/dsa-3446

Plugin Details

Severity: Medium

ID: 87934

File Name: debian_DSA-3446.nasl

Version: 2.11

Type: local

Agent: unix

Published: 2016/01/15

Modified: 2018/11/10

Dependencies: 12634

Risk Information

Risk Factor: Medium

CVSS v2.0

Base Score: 4.6

Temporal Score: 3.4

Vector: CVSS2#AV:N/AC:H/Au:S/C:P/I:P/A:P

Temporal Vector: CVSS2#E:U/RL:OF/RC:C

CVSS v3.0

Base Score: 8.1

Temporal Score: 7.1

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

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: p-cpe:/a:debian:debian_linux:openssh, cpe:/o:debian:debian_linux:7.0, cpe:/o:debian:debian_linux:8.0

Exploit Available: false

Exploit Ease: No known exploits are available

Patch Publication Date: 2016/01/14

Reference Information

CVE: CVE-2016-0777, CVE-2016-0778

DSA: 3446