FreeBSD kernel: Denial of Service -- Remote/Unauthenticated

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2018.2499
               Resource exhaustion in IP fragment reassembly
                              23 August 2018

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           FreeBSD kernel
Publisher:         FreeBSD
Operating System:  FreeBSD
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-6923  

Reference:         ESB-2018.2417
                   ESB-2018.2296.2

Original Bulletin: 
   http://www.vuxml.org/freebsd/359e1548-a652-11e8-805b-a4badb2f4699.html

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FreeBSD -- Resource exhaustion in IP fragment reassembly

Affected packages
11.2 <= FreeBSD-kernel < 11.2_2
11.1 <= FreeBSD-kernel < 11.1_13

Details

VuXML ID  359e1548-a652-11e8-805b-a4badb2f4699
Discovery 2018-08-14
Entry     2018-08-22

Problem Description:

A researcher has notified us of a DoS attack applicable to another operating
system. While FreeBSD may not be vulnerable to that exact attack, we have
identified several places where inadequate DoS protection could allow an
attacker to consume system resources.

It is not necessary that the attacker be able to establish two-way
communication to carry out these attacks. These attacks impact both IPv4 and
IPv6 fragment reassembly.

Impact:

In the worst case, an attacker could send a stream of crafted fragments with a
low packet rate which would consume a substantial amount of CPU.

Other attack vectors allow an attacker to send a stream of crafted fragments
which could consume a large amount of CPU or all available mbuf clusters on
the system.

These attacks could temporarily render a system unreachable through network
interfaces or temporarily render a system unresponsive. The effects of the
attack should clear within 60 seconds after the attack stops.

References

CVE Name         CVE-2018-6923
FreeBSD Advisory SA-18:10.ip

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