Subject: [ASA-201808-4] linux: denial of service

Arch Linux Security Advisory ASA-201808-4
=========================================

Severity: High
Date    : 2018-08-08
CVE-ID  : CVE-2018-5390
Package : linux
Type    : denial of service
Remote  : Yes
Link    : https://security.archlinux.org/AVG-747

Summary
=======

The package linux before version 4.17.11-1 is vulnerable to denial of
service.

Resolution
==========

Upgrade to 4.17.11-1.

# pacman -Syu "linux>=4.17.11-1"

The problem has been fixed upstream in version 4.17.11.

Workaround
==========

None.

Description
===========

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.

Impact
======

A remote attacker is able to saturate the CPU and hence cause a denial
of service on the host system by sending specially modified packets
within ongoing TCP sessions.

References
==========

https://www.kb.cert.org/vuls/id/962459
https://www.spinics.net/lists/netdev/msg514742.html
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=72cd43ba64fc172a443410ce01645895850844c8
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f4a3313d8e2ca9fd8d8f45e40a2903ba782607e7
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3d4bf93ac12003f9b8e1e2de37fe27983deebdcf
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=8541b21e781a22dce52a74fef0b9bed00404a1cd
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=58152ecbbcc6a0ce7fddd5bf5f6ee535834ece0c
https://security.archlinux.org/CVE-2018-5390