FreeBSD Security Advisories
2019-May-15 00:01 UTC
FreeBSD Security Advisory FreeBSD-SA-19:04.ntp
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================FreeBSD-SA-19:04.ntp Security Advisory The FreeBSD Project Topic: Authenticated denial of service in ntpd Category: contrib Module: ntp Announced: 2019-05-14 Credits: Magnus Stubman Affects: All supported versions of FreeBSD Corrected: 2019-03-07 13:45:36 UTC (stable/12, 12.0-STABLE) 2019-05-14 23:02:56 UTC (releng/12.0, 12.0-RELEASE-p4) 2019-03-07 13:45:36 UTC (stable/11, 11.3-PRERELEASE) 2019-05-14 23:06:26 UTC (releng/11.2, 11.2-RELEASE-p10) CVE Name: CVE-2019-8936 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>. I. Background The ntpd(8) daemon is an implementation of the Network Time Protocol (NTP) used to synchronize the time of a computer system to a reference time source. The ntpd(8) daemon uses a protocol called mode 6 to both get status information from the running ntpd(8) daemon and configure it on the fly. This protocol is typically used by the ntpq(8) program, among others. II. Problem Description A crafted malicious authenticated mode 6 packet from a permitted network address can trigger a NULL pointer dereference. Note for this attack to work, the sending system must be on an address from which the target ntpd(8) accepts mode 6 packets, and must use a private key that is specifically listed as being used for mode 6 authorization. III. Impact The ntpd daemon can crash due to the NULL pointer dereference, causing a denial of service. IV. Workaround Use 'restrict noquery' in the ntpd configuration to limit addresses that can send mode 6 queries. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date. 2) To update your vulnerable system via a binary patch: Systems running a RELEASE version of FreeBSD on the i386 or amd64 platforms can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install Afterwards, restart the ntpd service: # service ntpd restart 3) To update your vulnerable system via a source code patch: The following patches have been verified to apply to the applicable FreeBSD release branches. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. [FreeBSD 12.0] # fetch https://security.FreeBSD.org/patches/SA-19:04/ntp.patch # fetch https://security.FreeBSD.org/patches/SA-19:04/ntp.patch.asc # gpg --verify ntp.patch.asc [FreeBSD 11.2-RELEASE/11.3-PRERELEASE] # fetch https://security.FreeBSD.org/patches/SA-19:04/ntp-11.2.patch # fetch https://security.FreeBSD.org/patches/SA-19:04/ntp-11.2.patch.asc # gpg --verify ntp-11.2.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile the operating system using buildworld and installworld as described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>. Restart the ntpd service, or reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/12/ r344884 releng/12.0/ r347589 stable/11/ r344884 releng/11.2/ r347590 - ------------------------------------------------------------------------- To see which files were modified by a particular revision, run the following command, replacing NNNNNN with the revision number, on a machine with Subversion installed: # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base Or visit the following URL, replacing NNNNNN with the revision number: <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN> VII. References <URL:http://support.ntp.org/bin/view/Main/SecurityNotice#March_2019_ntp_4_2_8p13_NTP_Rele> <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-8936> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:04.ntp.asc> -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAlzbTrdfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cLGtw/8CNAYnLxARrMUK1QeC9sE7EaboYInSOgaunfK2Uw5tJk9b4GwWWjCSE0C hSWg4a9xv3pks2ppfEJzRuy0eoYmiU0MYblnAnCwCmE2d3WYlExO7hZJa1iK3uPO WvHre5q80kF8TJhS9rbph+6oyLaPun8f9PDIo4Oc2knTppNfrfzbB/HEuzP27KMp gCXD/Nk/5tHbXjkIGamWCf9wgYuw/typYRV3W6sWDuPhug2sAvWk1TMo0cMJ4BHL wL7Qh00rZ+nHWdk5GKFslga9gNjVPqD2DzRKCQO2bj4o+7ly2d+yk4jUpMKBq2r4 eQcQQnk9xj60NQ5cHGprOv6xwulBYycugF57iouNAP241cvVf+XZd4b/GthJODgz fhP0aquusmtkawida3ZWWIVCjkM5NmHQsY5VTQLvTudtemb3kdmRMy3dFDN7oyXZ PqP6JJUqamxNHilxRVytNCZLiSuy1P2MnJamyLZIqcDiT6yvMVBqwuGdQrSTSKyu g/sR+vUohuJrP2i3pCCEfGtH5Nfq6GpY6Swxec81wUoqReGVCGmSFSEaas21TFYf ZzAEAhywveGegkhqvsGP9A1zrTs6ZTCRzun32MhSo4xH/YZaArMvRa6JiSWTA1fG ctwXEwIBj0XNEWBsCPgVvaF9bglmQZ2Iqn4iOiHlRGT7KxgjT7w=o9t5 -----END PGP SIGNATURE-----