Arch Linux Security Advisory ASA-201504-9
========================================
Severity: Medium
Date    : 2015-04-08
CVE-ID  : CVE-2015-1853
Package : chrony
Type    : denial of service
Remote  : Yes
Link    : https://wiki.archlinux.org/title/CVE

Summary
======
The package chrony before version 1.31.1-1 is vulnerable to denial of service

Resolution
=========
Upgrade to 1.31.1-1

# pacman -Syu "chrony>=1.31.1-1"

The problem has been fixed upstream.

Workaround
=========
None.

Description
==========
CVE-2015-1853 (denial of service):
This issue is similiar to the "ntp CVE-2015-1799"-issue.
An attacker knowing that NTP hosts A and B are peering with each other
(symmetric association) can send a packet to host A with source address of B
which will set the NTP state variables on A to the values sent by the attacker.
Host A will then send on its next poll to B a packet with originate timestamp
that doesn't match the transmit timestamp of B and the packet will be dropped.
If the attacker does this periodically for both hosts, they won't be able to
synchronize to each other. This is a known denial-of-service attack

Impact
=====
CVE-2015-1853 (denial of service):

An attacker could stop the synchronizing process of chrony.

References
=========
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2015-1853
https://access.redhat.com/security/cve/CVE-2015-1853
https://seclists.org/oss-sec/2015/q2/63