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=====================================================================
                   Red Hat Security Advisory

Synopsis:          Important: kernel security and bug fix update
Advisory ID:       RHSA-2019:1489-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://access.redhat.com/errata/RHSA-2019:1489
Issue date:        2019-06-17
CVE Names:         CVE-2019-3896 CVE-2019-11477 CVE-2019-11478 
                   CVE-2019-11479 
=====================================================================

1. Summary:

An update for kernel is now available for Red Hat Enterprise Linux 6.6
Advanced Update Support.

Red Hat Product Security has rated this update as having a security impact
of Important. A Common Vulnerability Scoring System (CVSS) base score,
which gives a detailed severity rating, is available for each vulnerability
from the CVE link(s) in the References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux Server AUS (v. 6.6) - noarch, x86_64
Red Hat Enterprise Linux Server Optional AUS (v. 6.6) - x86_64

3. Description:

The kernel packages contain the Linux kernel, the core of any Linux
operating system.

Security Fix(es):

* An integer overflow flaw was found in the way the Linux kernel's
networking subsystem processed TCP Selective Acknowledgment (SACK)
segments. While processing SACK segments, the Linux kernel's socket buffer
(SKB) data structure becomes fragmented. Each fragment is about TCP maximum
segment size (MSS) bytes. To efficiently process SACK blocks, the Linux
kernel merges multiple fragmented SKBs into one, potentially overflowing
the variable holding the number of segments. A remote attacker could use
this flaw to crash the Linux kernel by sending a crafted sequence of SACK
segments on a TCP connection with small value of TCP MSS, resulting in a
denial of service (DoS). (CVE-2019-11477)

* kernel: Double free in lib/idr.c (CVE-2019-3896)

* Kernel: tcp: excessive resource consumption while processing SACK blocks
allows remote denial of service (CVE-2019-11478)

* Kernel: tcp: excessive resource consumption for TCP connections with low
MSS allows remote denial of service (CVE-2019-11479)

For more details about the security issue(s), including the impact, a CVSS
score, acknowledgments, and other related information, refer to the CVE
page(s) listed in the References section.

Bug Fix(es):

* MDS mitigations not enabled on Intel Skylake CPUs (BZ#1713026)

* [RHEL6] md_clear flag missing from /proc/cpuinfo (BZ#1713029)

* RHEL6 kernel does not disable SMT with mds=full,nosmt (BZ#1713044)

4. Solution:

For details on how to apply this update, which includes the changes
described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.

5. Bugs fixed (https://bugzilla.redhat.com/):

1694812 - CVE-2019-3896 kernel: Double free in lib/idr.c
1719123 - CVE-2019-11477 Kernel: tcp: integer overflow while processing SACK
 blocks allows remote denial of service
1719128 - CVE-2019-11478 Kernel: tcp: excessive resource consumption while
 processing SACK blocks allows remote denial of service
1719129 - CVE-2019-11479 Kernel: tcp: excessive resource consumption for TCP
 connections with low MSS allows remote denial of service

6. Package List:

Red Hat Enterprise Linux Server AUS (v. 6.6):

Source:
kernel-2.6.32-504.79.3.el6.src.rpm

noarch:
kernel-abi-whitelists-2.6.32-504.79.3.el6.noarch.rpm
kernel-doc-2.6.32-504.79.3.el6.noarch.rpm
kernel-firmware-2.6.32-504.79.3.el6.noarch.rpm

x86_64:
kernel-2.6.32-504.79.3.el6.x86_64.rpm
kernel-debug-2.6.32-504.79.3.el6.x86_64.rpm
kernel-debug-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm
kernel-debug-devel-2.6.32-504.79.3.el6.x86_64.rpm
kernel-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm
kernel-debuginfo-common-x86_64-2.6.32-504.79.3.el6.x86_64.rpm
kernel-devel-2.6.32-504.79.3.el6.x86_64.rpm
kernel-headers-2.6.32-504.79.3.el6.x86_64.rpm
perf-2.6.32-504.79.3.el6.x86_64.rpm
perf-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm
python-perf-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm

Red Hat Enterprise Linux Server Optional AUS (v. 6.6):

x86_64:
kernel-debug-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm
kernel-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm
kernel-debuginfo-common-x86_64-2.6.32-504.79.3.el6.x86_64.rpm
perf-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm
python-perf-2.6.32-504.79.3.el6.x86_64.rpm
python-perf-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm

These packages are GPG signed by Red Hat for security.  Our key and
details on how to verify the signature are available from
https://access.redhat.com/security/team/key/

7. References:

https://access.redhat.com/security/cve/CVE-2019-3896
https://access.redhat.com/security/cve/CVE-2019-11477
https://access.redhat.com/security/cve/CVE-2019-11478
https://access.redhat.com/security/cve/CVE-2019-11479
https://access.redhat.com/security/updates/classification/#important
https://access.redhat.com/security/vulnerabilities/tcpsack

8. Contact:

The Red Hat security contact is <secalert@redhat.com>. More contact
details at https://access.redhat.com/security/team/contact/

Copyright 2019 Red Hat, Inc.
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