Arch Linux Security Advisory ASA-201606-4 ========================================= Severity: High Date : 2016-06-04 CVE-ID : CVE-2016-4953 CVE-2016-4954 CVE-2016-4955 CVE-2016-4956 CVE-2016-4957 Package : ntp Type : distributed denial of service amplification Remote : Yes Link : https://wiki.archlinux.org/index.php/CVE Summary ======= The package ntp before version 4.2.8.p8-1 can be used to amplify distributed denial of service (DDoS) attacks. Resolution ========== Upgrade to 4.2.8.p8-1. # pacman -Syu "ntp>=4.2.8.p8-1" The problem has been fixed upstream in version 4.2.8.p8. Workaround ========== Implement ingress and egress filtering through BCP38. Description =========== - CVE-2016-4953 (distributed denial of service amplification) An attacker who knows the origin timestamp and can send a spoofed packet containing a CRYPTO-NAK to an ephemeral peer target before any other response is sent can demobilize that association. Credit to Miroslav Lichvar of Red Hat - CVE-2016-4954 (distributed denial of service amplification) An attacker who is able to spoof packets with correct origin timestamps from enough servers before the expected response packets arrive at the target machine can affect some peer variables and, for example, cause a false leap indication to be set. Credit to Jakub Prokes of Red Hat - CVE-2016-4955 (distributed denial of service amplification) An attacker who is able to spoof a packet with a correct origin timestamp before the expected response packet arrives at the target machine can send a CRYPTO_NAK or a bad MAC and cause the association's peer variables to be cleared. If this can be done often enough, it will prevent that association from working. Credit to Miroslav Lichvar of Red Hat - CVE-2016-4956 (distributed denial of service amplification) The fix for NtpBug2978 does not cover broadcast associations, so broadcast clients can be triggered to flip into interleave mode. Credit to Miroslav Lichvar of Red Hat - CVE-2016-4957 (distributed denial of service amplification) The fix for Sec 3007 in ntp-4.2.8p7 contained a bug that could cause ntpd to crash. Credit to Nicolas Edet of Cisco Impact ====== A remote attacker can utilize unpatched or improperly filtered NTP servers as participants in distributed denial of service attacks (DDoS). References ========== http://support.ntp.org/bin/view/Main/NtpBug3042 https://access.redhat.com/security/cve/cve-2016-4956 http://support.ntp.org/bin/view/Main/NtpBug3043 https://access.redhat.com/security/cve/cve-2016-4955 http://support.ntp.org/bin/view/Main/NtpBug3044 https://access.redhat.com/security/cve/cve-2016-4954 http://support.ntp.org/bin/view/Main/NtpBug3045 https://access.redhat.com/security/cve/cve-2016-4953 http://support.ntp.org/bin/view/Main/NtpBug3046 https://access.redhat.com/security/cve/cve-2016-4957