Debian DLA-387-1 : openssh security update

Medium Nessus Plugin ID 87933

Synopsis

The remote Debian host is missing a security 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 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.

- -- Yves-Alexis Perez

NOTE: Tenable Network Security has extracted the preceding description
block directly from the DLA security advisory. Tenable has attempted
to automatically clean and format it as much as possible without
introducing additional issues.

Solution

Upgrade the affected packages.

See Also

https://lists.debian.org/debian-lts-announce/2016/01/msg00010.html

https://packages.debian.org/source/squeeze-lts/openssh

Plugin Details

Severity: Medium

ID: 87933

File Name: debian_DLA-387.nasl

Version: 2.9

Type: local

Agent: unix

Published: 2016/01/15

Modified: 2018/07/09

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-client, p-cpe:/a:debian:debian_linux:openssh-client-udeb, p-cpe:/a:debian:debian_linux:openssh-server, p-cpe:/a:debian:debian_linux:openssh-server-udeb, p-cpe:/a:debian:debian_linux:ssh, p-cpe:/a:debian:debian_linux:ssh-askpass-gnome, p-cpe:/a:debian:debian_linux:ssh-krb5, cpe:/o:debian:debian_linux:6.0

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