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AUSCERT External Security Bulletin Redistribution
Resource exhaustion in IP fragment reassembly
23 August 2018
AusCERT Security Bulletin Summary
Product: FreeBSD kernel
Operating System: FreeBSD
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2018-6923
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FreeBSD -- Resource exhaustion in IP fragment reassembly
11.2 <= FreeBSD-kernel < 11.2_2
11.1 <= FreeBSD-kernel < 11.1_13
VuXML ID 359e1548-a652-11e8-805b-a4badb2f4699
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.
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
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.
CVE Name CVE-2018-6923
FreeBSD Advisory SA-18:10.ip
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