Title: EGI SVG 'ADVISORY' [TLP:WHITE] **UPDATE 3** HIGH risk - privilege
escalation vulnerability in recent kernels (e.g. RHEL/CentOS 8)
[EGI-SVG-CVE-2020-14386]
Date: 2020-09-22
Updated: 2020-10-22, 2020-10-28
Affected software and risk
==========================
HIGH risk vulnerability in recent kernels, used e.g. by RHEL 8 and derivatives
Package : Linux kernel used e.g. by RHEL 8 and derivatives
CVE ID : CVE-2020-14386
Bug ID : RedHat Bugzilla 1875699
A memory corruption vulnerability described in CVE-2020-14386 [R 1], [R 2] has
been found in some versions of the Linux kernel that may result in privilege
escalation to gain root privileges from unprivileged processes.
Specifically, this affects RedHat Enterprise Linux 8 and its derivatives
including CentOS 8; RHEL 7 and CentOS 7 are not affected.
Actions required/recommended
============================
**UPDATE 2020-10-22**
RedHat has fixed this issue - see [R 8], fixes are now available for RedHat and
its derivatives.
Sites are recommended to update relevant components. This should be carried
out urgently if they have not already carried out the mitigation described in
this advisory on affected hosts, especially those providing shell or container
access to unprivileged users.
Sites should be aware that if a public exploit is released which demonstrates a
root exploit of this vulnerability this vulnerability is likely to be elevated
to 'Critical' and sites will then be required to take action within 7 days or
risk suspension.
In general, the EGI SVG recommends that sites enable user namespaces (an
advisory was issued on this [R 3]).
**UPDATE 2020-10-28 ** We refer to the latest OSG recommendations and
information on network and user namespaces, and their relationship with the
more recent kernels [R 9]
Based on the latest OSG recommendation
======================================
Additionally, the OSG Security team and the EGI SVG recommend disabling network
namespaces when unprivileged user namespaces are enabled [R 3]:
echo “user.max_net_namespaces = 0” \
/etc/sysctl.d/90-max_net_namespaces.conf sysctl -p /etc/sysctl.d/90-max_net_namespaces.conf
Note that docker uses network namespaces, unless it is invoked with --net=host.
Disabling network namespaces also blocks the systemd PrivateNetwork feature,
which is a feature that is used by some EL 8 services. It is also configured
for some EL 7 services but they are all disabled by default. More details on
this issue and potential workarounds are available in the OSG Singularity
documentation [R 9].
Unprivileged user namespaces are enabled by default on EL8. If you are not
using unprivileged user namespaces (for example for singularity), you can also
mitigate this issue by disabling them:
echo “user.max_user_namespaces = 0” \
/etc/sysctl.d/90-max_user_namespaces.conf sysctl -p /etc/sysctl.d/90-max_user_namespaces.conf
Note RHEL/CentOS 8, recent Fedora versions, Debian, Ubuntu and OpenSUSE (LEAP
15.1 and newer) have user namespaces enabled by default.
Component installation information
==================================
For information related to RedHat see [R 2]
For information related to Debian see [R 4]
For information related to Ubuntu see [R 5]
Mitigation
==========
**UPDATE 2020-10-22** A patched kernel is now available. This mitigation was
the recommended action prior to the availability of a patched kernel.
The Red Hat security announcement [R 2] recommends disabling the CAP_NET_RAW
capability for regular users and executables as a mitigation.
Affected software details
=========================
RHEL 8 and CentOS 8 are affected.
RHEL 6 and RHEL 7 and their derivatives are not affected.
For information on Debian related to this specific vulnerability see [R 4], and
Ubuntu see [R 5]
More information
================
A memory corruption vulnerability [R 6] exists in code related to handling
AF_PACKET sockets. An unprivileged user on systems where unprivileged user
namespaces are enabled, such as EL8 systems, can acquire the CAP_NET_RAW
capability to create AF_PACKET sockets and trigger this memory corruption,
potentially leading to privilege escalation.
At present, only crashing of services has been demonstrated as a result of
exploit of this vulnerability, but we are aware of on-going efforts to develop
a root exploit of this vulnerability. Previously memory corruption
vulnerabilities where only an operational risk was initially demonstrated have
later been associated with incidents.
Some sites have found that setting "user.max_net_namespaces = 0" as
recommended breaks some features with some of the latest kernels.
OSG has since looked at this and modified its recommendations and we refer
sites to OSG information at [R 9].
TLP and URL
===========
** WHITE information - Unlimited distribution
- see https://go.egi.eu/tlp for distribution restrictions **
URL: https://advisories.egi.eu/Advisory-SVG-CVE-2020-14386
Minor updates may be made without re-distribution to the sites
Comments
========
Comments or questions should be sent to svg-rat at mailman.egi.eu
If you find or become aware of another 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 according to the
procedure defined in [R 7]
Note that this is undergoing revision to fully handle vulnerabilities in the
EOSC-hub era.
References
==========
[R 1] https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-14386
[R 2] https://access.redhat.com/security/cve/CVE-2020-14386
[R 3] https://advisories.egi.eu/Advisory-SVG-2020-16648
[R 4] https://security-tracker.debian.org/tracker/CVE-2020-14386
[R 5] https://people.canonical.com/~ubuntu-security/cve/2020/CVE-2020-14386
[R 6] https://seclists.org/oss-sec/2020/q3/146
[R 7] https://documents.egi.eu/public/ShowDocument?docid=3145
[R 8] https://access.redhat.com/errata/RHSA-2020:4286
[R 9] https://opensciencegrid.org/docs/worker-node/install-singularity/#enabling-unprivileged-singularity
Credit
======
SVG was alerted to this vulnerability by Dave Dykstra
Some of the information in this advisory is based on the corresponding OSG
advisory for these vulnerabilities.
Timeline
========
Yyyy-mm-dd [EGI-SVG-CVE-2020-14386]
2020-09-17 SVG alerted to this issue by Dave Dykstra
2020-09-18 Acknowledgement from the EGI SVG to the reporter
2020-09-18 Investigation of vulnerability and relevance to EGI carried out
2020-09-21 EGI SVG Risk Assessment completed
2020-09-22 Advisory sent to sites recommending mitigating action
2020-10-22 Advisory updated as issue has been fixed and sites are recommended
to update
2020-10-28 Advisory updated to include the latest OSG recommendations.
Context
=======
This advisory has been prepared as part of the effort to fulfil EGI SVG's
purpose "To minimize the risk to the EGI infrastructure arising from software
vulnerabilities"
The risk is that assessed by the group, according to the EGI SVG issue handling
procedure [R 7] in the context of how the software is used in the EGI
infrastructure. It is the opinion of the group, we do not guarantee it to be
correct. The risk may also be higher or lower in other deployments depending
on how the software is used.
-----------------------------
This advisory is subject to the Creative commons license
https://creativecommons.org/licenses/by/4.0/ and the EGI https://www.egi.eu/
Software Vulnerability Group must be credited.
-----------------------------
Note that the SVG issue handling procedure is currently under review, to take
account of the increasing inhomogeneity of the EGI infrastructure and the
services in the EOSC-hub catalogue.
On behalf of the EGI SVG,