Advisory-SVG-CVE-2016-5195


Title:       EGI SVG 'Heads up'[TLP:WHITE ] 'CRITICAL' Risk CVE-2016-5195 
             Linux kernel privilege escalation [EGI-SVG-CVE-2016-5195] 

Date:        2016-10-20
Updated:     2016-10-23 (Wiki only) 2016-10-24 

Affected software and risk
==========================

CRITICAL risk vulnerability concerning Linux kernel

Package : Linux Kernel
CVE ID  : CVE-2016-5195

A kernel vulnerability has been found concerning a race condition allowing an unprivileged local user 
to gain write access to otherwise read only mappings and increase their privilege in the system. 

** UPDATE 24th October 2016 **
============================

Since the vulnerability was publicly announced last week, publicly available exploits have emerged and are trivial 
to use to gain root on the affected systems. Unlike the initial exploit, some exploits were reported to work with
 RHEL5/6 systems (using 'PTRACE_POKEDATA') see [R 6].

At the time of writing, there is still no official update from RedHat.

As a result, we urge EGI sites to take immediate actions to mitigate the vulnerability from their systems or to 
declare a downtime (for details see below) and close any public interfaces used by VOs or users.
Such downtime will not be counted for the availability of your site until 3 working days after a patch is released 
and an advisory update is circulated.

Actions required/recommended
============================

Sites running an OS where patches are available (currently Debian and
Ubuntu) are required to install the new version. Machines allowing unprivileged user access, such as Grid Worker Nodes, 
should be prioritised.

Sites running an OS where patches are not available are required to deploy a mitigation or to declare a downtime in GOC-DB 
with the words 'EGI-SVG-CVE-2016-5195, vulnerability handling in progress' and close their site until a patch or mitigation 
is deployed. Machines allowing unprivileged user access, such as Grid Worker Nodes or User Interfaces, should be prioritised.

Sites failing to act and/or failing to respond to requests from the EGI CSIRT team before 2016-10-27T15:00:00Z risk site suspension.

Known Mitigations
=================

The following mitigations are known to work on RedHat-based distributions:

- A system-tap module that disable /proc/self/mem and ptrace, the official RedHat mitigation,
https://bugzilla.redhat.com/show_bug.cgi?id=1384344#c13 (no reboot needed). Please note that this compltely disable GDB:
* If you use Centos 7 or Scientific Linux CERN 6, CERN is providing pre-compiled modules:
https://cern.service-now.com/service-portal/view-outage.do?n=OTG0033700
* If you use Centos 6, Nikhef is providing a pre-compiled module:
https://software.nikhef.nl/experimental/cve_2016_5195/
* If you are using Scientific Linux 6 or other flavor, there is currently no known pre-compiled module, you can compile some yourself.
Examples available here:
https://gitlab.cern.ch/ComputerSecurity/cve_2016_5195/tree/master

- A kernel module that disable the 'madvise' system call, the main component of the vulnerability exploit. 
CESNET provides an implementation of the module at https://github.com/bodik/dirtyc0w/tree/master/nomadvise (no reboot needed)

- The upstream patch has been ported to the Centos 6 kernel, resulting in a non vulnerable kernel: http://rep.grid.kiae.ru/pub/cve-2016-5195/

Affected software details
=========================

All Linux distributions, see relevant OS providers.

More information
================

More information is available from RedHat [R 1]

This advisory will be updated when patches become available for more different operating systems.

Component installation information
==================================

Sites running Debian should see [R 2]

Sites running Ubuntu should see [R 3]

Sites running RedHat should see [R 4] (patch not available at time of
writing)

Sites running Scientific Linux (SL) should see [R 5] (patch not available at time of writing)

TLP and URL
===========

** WHITE information - Unlimited distribution - see

https://wiki.egi.eu/wiki/EGI_CSIRT:TLP for distribution restrictions***

URL: https://wiki.egi.eu/wiki/SVG:Advisory-SVG-CVE-2016-5195

Minor updates may be made without re-distribution to the sites, major updates will be sent by mail. 
Sites are encouraged to check this URL frequently until the situation is resolved.

Credit
======

SVG was alerted to this vulnerability by Daniel Kouril

References
==========

[R 1] https://bugzilla.redhat.com/show_bug.cgi?id=1384344

[R 2] https://security-tracker.debian.org/tracker/CVE-2016-5195

[R 3]
http://people.canonical.com/~ubuntu-security/cve/2016/CVE-2016-5195.html

[R 4] https://access.redhat.com/security/cve/CVE-2016-5195

[R 5] https://www.scientificlinux.org/

[R 6] https://github.com/dirtycow/dirtycow.github.io/wiki/PoCs

Comments
========

Comments or questions should be sent to svg-rat at mailman.egi.eu

If you find or become aware of a vulnerability which is relevant to EGI you may report it by e-mail to 

report-vulnerability at egi.eu. 

The EGI Software Vulnerability Group will take a look.

Timeline
========
Yyyy-mm-dd [EGI-SVG-CVE-2016-5195]

2016-10-20 SVG alerted to this issue by Daniel Kouril
2016-10-20 Investigation of vulnerability and relevance to EGI
2016-10-20 EGI SVG Risk Assessment completed
2016-10-20 IRTF/SVG agreed to issue an urgent heads up.
2016-10-20 'Heads up' sent to sites
2016-10-24 Update sent to sites, clarifying actions
SVG:Advisory-SVG-CVE-2016-5195

Advisory-SVG-CVE-2016-5195

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