Bug 1363710 (CVE-2016-6301) - CVE-2016-6301 busybox: NTP server denial of service flaw
Summary: CVE-2016-6301 busybox: NTP server denial of service flaw
Alias: CVE-2016-6301
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On: 1363711
Blocks: Embargoed1363714
TreeView+ depends on / blocked
Reported: 2016-08-03 12:11 UTC by Martin Prpič
Modified: 2021-02-17 03:28 UTC (History)
4 users (show)

Fixed In Version:
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Last Closed: 2016-08-05 09:05:24 UTC

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Description Martin Prpič 2016-08-03 12:11:59 UTC
The busybox NTP implementation doesn't check the NTP mode of packets received on the server port and responds to any packet with the right size. This includes responses from another NTP server. An attacker can send a packet with a spoofed source address in order to create an infinite loop of responses between two busybox NTP servers. Adding more packets to the loop increases the traffic between the servers until one of them has a fully loaded CPU and/or network.

It seems this bug was actually inherited from openntpd, on which the busybox implementation was based on. In openntpd it was fixed in:


Busybox upstream patch:


Comment 1 Martin Prpič 2016-08-03 12:12:08 UTC

Name: Miroslav Lichvar (Red Hat)

Comment 2 Martin Prpič 2016-08-03 12:12:22 UTC
Created busybox tracking bugs for this issue:

Affects: fedora-all [bug 1363711]

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