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AUSCERT External Security Bulletin Redistribution
ntp -- Crafted null dereference attack from a trusted source
with an authenticated mode 6 packet
8 March 2019
AusCERT Security Bulletin Summary
Operating System: FreeBSD
UNIX variants (UNIX, Linux, OSX)
Impact/Access: Denial of Service -- Existing Account
CVE Names: CVE-2019-8936
Comment: This advisory references vulnerabilities in products which run on
platforms other than FreeBSD. It is recommended that administrators
running ntp check for an updated version of the software for their
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ntp -- Crafted null dereference attack from a trusted source with an
authenticated mode 6 packet
ntp < 4.2.8p13
12.0 <= FreeBSD < 12.0_2
11.2 <= FreeBSD < 11.2_8
VuXML ID c2576e14-36e2-11e9-9eda-206a8a720317
Network Time Foundation reports:
A crafted malicious authenticated mode 6 (ntpq) packet from a permitted
network address can trigger a NULL pointer dereference, crashing ntpd.
Note that for this attack to work, the sending system must be on an address
that the target's ntpd accepts mode 6 packets from, and must use a private
key that is specifically listed as being used for mode 6 authorization.
Impact: The ntpd daemon can crash due to the NULL pointer dereference,
causing a denial of service.
o Use restrict noquery to limit addresses that can send mode 6 queries.
o Limit access to the private controlkey in ntp.keys.
o Upgrade to 4.2.8p13, or later.
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