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Category:   OS (Linux)  >   Linux Kernel Vendors:   kernel.org
(Red Hat Issues Fix) Linux Kernel TCP Reassembly Algorithm Lets Remote Users Consume Excessive CPU Resources on the Target System
SecurityTracker Alert ID:  1041722
SecurityTracker URL:  http://securitytracker.com/id/1041722
CVE Reference:   CVE-2018-5390   (Links to External Site)
Updated:  Sep 25 2018
Original Entry Date:  Sep 25 2018
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): RHEL 6, 6.4, 7.2, 7.3, and 7.4
Description:   A vulnerability was reported in the Linux kernel. A remote user can consume excessive CPU resources on the target system.

The system uses an inefficient TCP reassembly algorithm. A remote user can send specially crafted data via an established TCP connection to consume excessive CPU resources on the target system.

Juha-Matti Tilli (Aalto University, Department of Communications and Networking / Nokia Bell Labs) reported this vulnerability.

Impact:   A remote user can consume excessive CPU resources on the target system.
Solution:   Red Hat has issued a fix.

The Red Hat advisories are available at:

https://access.redhat.com/errata/RHSA-2018:2776
https://access.redhat.com/errata/RHSA-2018:2785
https://access.redhat.com/errata/RHSA-2018:2789
https://access.redhat.com/errata/RHSA-2018:2790
https://access.redhat.com/errata/RHSA-2018:2791

Vendor URL:  access.redhat.com/errata/RHSA-2018:2789 (Links to External Site)
Cause:   Resource error

Message History:   This archive entry is a follow-up to the message listed below.
Aug 7 2018 Linux Kernel TCP Reassembly Algorithm Lets Remote Users Consume Excessive CPU Resources on the Target System



 Source Message Contents

Subject:  [RHSA-2018:2789-01] Important: kernel-rt security and bug fix update

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

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

Synopsis:          Important: kernel-rt security and bug fix update
Advisory ID:       RHSA-2018:2789-01
Product:           Red Hat Enterprise MRG for RHEL-6
Advisory URL:      https://access.redhat.com/errata/RHSA-2018:2789
Issue date:        2018-09-25
CVE Names:         CVE-2018-5390 
=====================================================================

1. Summary:

An update for kernel-rt is now available for Red Hat Enterprise MRG 2.

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 MRG Realtime for RHEL 6 Server v.2 - noarch, x86_64

3. Description:

The kernel-rt packages provide the Real Time Linux Kernel, which enables
fine-tuning for systems with extremely high determinism requirements.

Security Fix(es):

* A flaw named SegmentSmack was found in the way the Linux kernel handled
specially crafted TCP packets. A remote attacker could use this flaw to
trigger time and calculation expensive calls to tcp_collapse_ofo_queue()
and tcp_prune_ofo_queue() functions by sending specially modified packets
within ongoing TCP sessions which could lead to a CPU saturation and hence
a denial of service on the system. Maintaining the denial of service
condition requires continuous two-way TCP sessions to a reachable open
port, thus the attacks cannot be performed using spoofed IP addresses.
(CVE-2018-5390)

Red Hat would like to thank Juha-Matti Tilli (Aalto University - Department
of Communications and Networking and Nokia Bell Labs) for reporting this
issue.

Bug Fix(es):

* The kernel-rt packages have been upgraded to the 3.10.0-693.39.1 source
tree, which provides a number of bug fixes over the previous version.
(BZ#1616431)

* Previously, preemption was enabled too early after a context switch. If a
task was migrated to another CPU after a context switch, a mismatch between
CPU and runqueue during load balancing sometimes occurred. Consequently, a
runnable task on an idle CPU failed to run, and the operating system became
unresponsive. This update disables preemption in the schedule_tail()
function. As a result, CPU migration during post-schedule processing no
longer occurs, which prevents the above mismatch. The operating system no
longer hangs due to this bug. (BZ#1618466)

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/):

1601704 - CVE-2018-5390 kernel: TCP segments with random offsets allow a remote denial of service (SegmentSmack)
1616431 - update the MRG 2.5.z 3.10 kernel-rt sources
1618466 - RT system hang due to wrong of rq's nr_running [MRG-RT]

6. Package List:

Red Hat MRG Realtime for RHEL 6 Server v.2:

Source:
kernel-rt-3.10.0-693.39.1.rt56.629.el6rt.src.rpm

noarch:
kernel-rt-doc-3.10.0-693.39.1.rt56.629.el6rt.noarch.rpm
kernel-rt-firmware-3.10.0-693.39.1.rt56.629.el6rt.noarch.rpm

x86_64:
kernel-rt-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-debug-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-debug-debuginfo-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-debug-devel-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-debuginfo-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-debuginfo-common-x86_64-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-devel-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-trace-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-trace-debuginfo-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-trace-devel-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-vanilla-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-vanilla-debuginfo-3.10.0-693.39.1.rt56.629.el6rt.x86_64.rpm
kernel-rt-vanilla-devel-3.10.0-693.39.1.rt56.629.el6rt.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-2018-5390
https://access.redhat.com/security/updates/classification/#important

8. Contact:

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

Copyright 2018 Red Hat, Inc.
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