Arch Linux Security Advisory ASA-201611-28 ========================================== Severity: High Date : 2016-11-26 CVE-ID : CVE-2016-7426 CVE-2016-7427 CVE-2016-7428 CVE-2016-7429 CVE-2016-7431 CVE-2016-7433 CVE-2016-7434 CVE-2016-9310 CVE-2016-9311 Package : ntp Type : multiple issues Remote : Yes Link : https://wiki.archlinux.org/index.php/CVE Summary ======= The package ntp before version 4.2.8.p9-1 is vulnerable to multiple issues including denial of service, insufficient validation and incorrect calculation. Resolution ========== Upgrade to 4.2.8.p9-1. # pacman -Syu "ntp>=4.2.8.p9-1" The problems have been fixed upstream in version 4.2.8.p9. Workaround ========== A partial fix to some of the issues is to implement BCP-38, use "restrict default noquery ..." in your ntp.conf file and only allow mode 6 queries from trusted networks and hosts. Description =========== - CVE-2016-7426 (denial of service) When ntpd is configured with rate limiting for all associations (restrict default limited in ntp.conf), the limits are applied also to responses received from its configured sources. An attacker who knows the sources (e.g., from an IPv4 refid in server response) and knows the system is (mis)configured in this way can periodically send packets with spoofed source address to keep the rate limiting activated and prevent ntpd from accepting valid responses from its sources. - CVE-2016-7427 (denial of service) The broadcast mode of NTP is expected to only be used in a trusted network. If the broadcast network is accessible to an attacker, a potentially exploitable denial of service vulnerability in ntpd's broadcast mode replay prevention functionality can be abused. An attacker with access to the NTP broadcast domain can periodically inject specially crafted broadcast mode NTP packets into the broadcast domain which, while being logged by ntpd, can cause ntpd to reject broadcast mode packets from legitimate NTP broadcast servers. - CVE-2016-7428 (denial of service) The broadcast mode of NTP is expected to only be used in a trusted network. If the broadcast network is accessible to an attacker, a potentially exploitable denial of service vulnerability in ntpd's broadcast mode poll interval enforcement functionality can be abused. To limit abuse, ntpd restricts the rate at which each broadcast association will process incoming packets. ntpd will reject broadcast mode packets that arrive before the poll interval specified in the preceding broadcast packet expires. An attacker with access to the NTP broadcast domain can send specially crafted broadcast mode NTP packets to the broadcast domain which, while being logged by ntpd, will cause ntpd to reject broadcast mode packets from legitimate NTP broadcast servers. - CVE-2016-7429 (denial of service) When ntpd receives a server response on a socket that corresponds to a different interface than was used for the request, the peer structure is updated to use the interface for new requests. If ntpd is running on a host with multiple interfaces in separate networks and the operating system doesn't check source address in received packets (e.g. rp_filter on Linux is set to 0), an attacker that knows the address of the source can send a packet with spoofed source address which will cause ntpd to select wrong interface for the source and prevent it from sending new requests until the list of interfaces is refreshed, which happens on routing changes or every 5 minutes by default. If the attack is repeated often enough (once per second), ntpd will not be able to synchronize with the source. - CVE-2016-7431 (insufficient validation) Zero Origin timestamp problems were fixed by Bug 2945 in ntp-4.2.8p6. However, subsequent timestamp validation checks introduced a regression in the handling of some Zero origin timestamp checks. - CVE-2016-7433 (incorrect calculation) ntpd Bug 2085 described a condition where the root delay was included twice, causing the jitter value to be higher than expected. Due to a misinterpretation of a small-print variable in The Book, the fix for this problem was incorrect, resulting in a root distance that did not include the peer dispersion. The calculations and formula have been reviewed and reconciled, and the code has been updated accordingly. - CVE-2016-7434 (denial of service) If ntpd is configured to allow mrulist query requests from a server that sends a crafted malicious packet, ntpd will crash on receipt of that crafted malicious mrulist query packet. - CVE-2016-9310 (denial of service) An exploitable configuration modification vulnerability exists in the control mode (mode 6) functionality of ntpd. If, against long-standing BCP recommendations, "restrict default noquery ..." is not specified, a specially crafted control mode packet can set ntpd traps, providing information disclosure and DDoS amplification, and unset ntpd traps, disabling legitimate monitoring. A remote, unauthenticated, network attacker can trigger this vulnerability. - CVE-2016-9311 (denial of service) ntpd does not enable trap service by default. If trap service has been explicitly enabled, an attacker can send a specially crafted packet to cause a null pointer dereference that will crash ntpd, resulting in a denial of service. Impact ====== A remote unauthenticated attacker may be able to perform a denial of service attack on ntpd via multiple vectors. References ========== http://support.ntp.org/bin/view/Main/SecurityNotice#November_2016_ntp_4_2_8p... http://www.kb.cert.org/vuls/id/633847 http://support.ntp.org/bin/view/Main/NtpBug3071 http://support.ntp.org/bin/view/Main/NtpBug3114 http://support.ntp.org/bin/view/Main/NtpBug3113 http://support.ntp.org/bin/view/Main/NtpBug3072 http://support.ntp.org/bin/view/Main/NtpBug3102 http://support.ntp.org/bin/view/Main/NtpBug3067 http://bugs.ntp.org/show_bug.cgi?id=2085 http://support.ntp.org/bin/view/Main/NtpBug3082 http://support.ntp.org/bin/view/Main/NtpBug3118 http://support.ntp.org/bin/view/Main/NtpBug3119 https://access.redhat.com/security/cve/CVE-2016-7426 https://access.redhat.com/security/cve/CVE-2016-7427 https://access.redhat.com/security/cve/CVE-2016-7428 https://access.redhat.com/security/cve/CVE-2016-7429 https://access.redhat.com/security/cve/CVE-2016-7431 https://access.redhat.com/security/cve/CVE-2016-7433 https://access.redhat.com/security/cve/CVE-2016-7434 https://access.redhat.com/security/cve/CVE-2016-9310 https://access.redhat.com/security/cve/CVE-2016-9311