Bug 1208684 (CVE-2014-9715)

Summary: CVE-2014-9715 kernel: netfilter connection tracking extensions denial of service
Product: [Other] Security Response Reporter: Fabio Olive Leite <fleite>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: agordeev, ajb, aquini, bhu, dhoward, fhrbata, jkacur, kernel-mgr, kstutsma, lgoncalv, lwang, mguzik, nmurray, phil, pholasek, plougher, pmatouse, ppandit, rvrbovsk, security-response-team, shuali, toracat, williams, wmealing
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
An integer overflow flaw was found in the way the Linux kernel's netfilter connection tracking implementation loaded extensions. An attacker on a local network could potentially send a sequence of specially crafted packets that would initiate the loading of a large number of extensions, causing the targeted system in that network to crash.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2015-08-26 11:15:45 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1206164, 1210157, 1210158, 1211096, 1241977, 1257147    
Bug Blocks: 1208686    

Description Fabio Olive Leite 2015-04-02 20:27:28 UTC 
Nathan Hoad reported that RHEL-7's kernel is affected by a netfilter NULL
pointer dereference that was fixed upstream on Linux 3.15.

A flaw was found in the method which the kernel handles netfilter connection tracking accounting.  The values stored the size of the extensions loaded, in some cases this may be all extensions and overflowing the len value.  The work-around solution was to modify the size of the value to accommodate the possibility of all extensions being loaded.

A user behind the NAT could potentially craft a sequence of packets to load extensions and to create a denial of service by crashing the system.

References:
http://marc.info/?l=netfilter-devel&m=140112364215200&w=2

The flaw was introduced on Linux 3.6 and fixed on 3.15, so Current Fedora
kernels are not affected. RHEL-5 and RHEL-6 kernels are also not affected.

Upstream fix:
-------------
 -> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=223b02d923ecd7c84cf9780bb3686f455d279279

References:
-----------
 -> http://marc.info/?l=netfilter-devel&m=140112364215200&w=2
 -> https://bugzilla.redhat.com/show_bug.cgi?id=1206164
 -> http://www.openwall.com/lists/oss-security/2015/04/08/1

Possible mitigation:
--------------------

Connection tracking accounting can be disabled at run time via a sysctl setting.


Runtime change:

This can be changed during runtime by running the following commands:

# echo 0 > /proc/sys/net/netfilter/nf_conntrack_acct

Persistent change:

To make this behaviour persistent across reboots, modify /etc/sysctl.conf and make the following change prior to reboot:

net.netfilter.nf_conntrack_acct = 0
Comment 2 Wade Mealing 2015-04-07 23:55:10 UTC 
*** Bug 1209314 has been marked as a duplicate of this bug. ***
Comment 3 Wade Mealing 2015-04-08 05:55:05 UTC 
Statement: 

This issue does not affect the versions of the Linux kernel as shipped with Red Hat Enterprise Linux 5 and 6. This issue affects the versions of the Linux kernel as shipped with Red Hat Enterprise Linux 7 and Red Hat Enterprise MRG 2.

For additional information, refer to the Red Hat Enterprise Linux Life Cycle: https://access.redhat.com/support/policy/updates/errata/.
Comment 4 Wade Mealing 2015-04-08 05:58:02 UTC 
Acknowledgements:

Red Hat would like to thank Nathan Hoad for reporting this issue.
Comment 11 errata-xmlrpc 2015-08-05 18:49:38 UTC 
This issue has been addressed in the following products:

  MRG for RHEL-6 v.2

Via RHSA-2015:1564 https://rhn.redhat.com/errata/RHSA-2015-1564.html
Comment 12 errata-xmlrpc 2015-08-05 20:13:52 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:1565 https://access.redhat.com/errata/RHSA-2015:1565
Comment 13 errata-xmlrpc 2015-08-06 02:42:57 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:1534 https://rhn.redhat.com/errata/RHSA-2015-1534.html