Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2016.0117.2 ntp panic threshold bypass vulnerability 15 January 2016 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: ntp Publisher: FreeBSD Operating System: FreeBSD Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2015-5300 Reference: ESB-2015.2694 Original Bulletin: https://www.freebsd.org/security/advisories/FreeBSD-SA-16:02.ntp.asc Revision History: January 15 2016: Changed original URL field. January 15 2016: Initial Release - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-16:02.ntp Security Advisory The FreeBSD Project Topic: ntp panic threshold bypass vulnerability Category: contrib Module: ntp Announced: 2016-01-14 Credits: Network Time Foundation Affects: All supported versions of FreeBSD. Corrected: 2016-01-11 01:09:50 UTC (stable/10, 10.2-STABLE) 2016-01-14 09:10:46 UTC (releng/10.2, 10.2-RELEASE-p9) 2016-01-14 09:11:16 UTC (releng/10.1, 10.1-RELEASE-p26) 2016-01-11 01:48:16 UTC (stable/9, 9.3-STABLE) 2016-01-14 09:11:26 UTC (releng/9.3, 9.3-RELEASE-p33) CVE Name: CVE-2015-5300 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. II. Problem Description The ntpd(8) daemon has a safety feature to prevent excessive stepping of the clock called the "panic threshold". If ever ntpd(8) determines the system clock is incorrect by more than this threshold, the daemon exits. There is an implementation error within the ntpd(8) implementation of this feature, which allows the system time be adjusted in certain circumstances. III. Impact When ntpd(8) is started with the '-g' option specified, the system time will be corrected regardless of if the time offset exceeds the panic threshold (by default, 1000 seconds). The FreeBSD rc(8) subsystem allows specifying the '-g' option by either including '-g' in the ntpd_flags list or by enabling ntpd_sync_on_start in the system rc.conf(5) file. If at the moment ntpd(8) is restarted, an attacker can immediately respond to enough requests from enough sources trusted by the target, which is difficult and not common, there is a window of opportunity where the attacker can cause ntpd(8) to set the time to an arbitrary value. IV. Workaround No workaround is available, but systems not running ntpd(8), or running ntpd(8) but do not use ntpd_sync_on_start="YES" or specify the '-g' option in ntpd_flags are not affected. Neither of these are set by default. 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. The ntpd service has to be restarted after the update. A reboot is recommended but not required. 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 The ntpd service has to be restarted after the update. A reboot is recommended but not required. 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 10.1 and 10.2] # fetch https://security.FreeBSD.org/patches/SA-16:02/ntp-10.patch # fetch https://security.FreeBSD.org/patches/SA-16:02/ntp-10.patch.asc # gpg --verify ntp-10.patch.asc [FreeBSD 9.3] # fetch https://security.FreeBSD.org/patches/SA-16:02/ntp-9.patch # fetch https://security.FreeBSD.org/patches/SA-16:02/ntp-9.patch.asc # gpg --verify ntp-9.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 applicable daemons, or reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - - ------------------------------------------------------------------------- stable/9/ r293652 releng/9.3/ r293896 stable/10/ r293650 releng/10.1/ r293894 releng/10.2/ r293893 - - ------------------------------------------------------------------------- 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:https://www.cs.bu.edu/~goldbe/NTPattack.html> <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-5300> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:02.ntp.asc> - -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJWl2j2AAoJEO1n7NZdz2rnyg4QAJ/x3xs+pNGXxTT63hbBqLcB NTSljW5+hFpL94Nr+rHrelvcT3HkvdWUC+7BvMksoUYCZv0vClp5W7tsfuojDPr0 GechK1BpLwxeLnRexulWEuvDQpbr6BN9ABdfSl4h3AaUwGYbBVLMY8aT5JpTiE3I UZg/5iPXVGFPcfdFhzaPgCpZxQtGI3QV7m5jx+Pf8r0ifuTNi8bAbwHCRzmOV8rA 1LM4fvlCPd6TiP3UANWM7PFGbX8UArgzXlb8jSwkxEVC02oZitol4UhcLgacwVrO 0/0q71pyn8W3NBQ1QPUaUg1M81sE501NCTCP3rEg+o6g7oxiq+GpgB0FKwCJxrTk n3EL7tyhbvVcsglPLRkIXkGz3o5XdelFJ66+qS+mZAiPozkzEFUIdxd8rHKsA1e4 ZIFARDvDgi8iTArbJnPsQH0CgK8+/2RV2ILFW00Zcu7batvSWJtAUNNFqTSN34tk JJzHWYwKfGwRIMyEABsy9wLez9K2tRIG0fX75p82dVbRcRZwwSfPmFdfDPuMRRmc dsNF3133TA92uxwZ177cZk537g+Q0/0I6bts8us3GlCdY2HBuIc+HvRJQyEEqGEv v1GfEdnwGLp4rmPI8uY+JQ87now7KYhAK1SVil9AXm3tLrIqJsHYayA9nI8mjxfY Mh1utEeP+TMuievDMQNo =il8c - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBVphjsn6ZAP0PgtI9AQLZQhAArtxThrA9eUCz80ZirLmPg3IBsvC1SZyZ GX5Rp4RNYsnXUeK13RKZlPcKTCHf5I8NzeGNoqxtYHi1/BPAM87T4NS35SjhpDzR 7qH7Q94Wymzd4HLBW5Hktw7V/lzOJR4g1swxb5NfmP1zkCSlA8OZRKHofGTMzUDA AMxl+GOUEoG//Qv58oJvHm4x7Xy11LiVUa51ViauaURqNGZbH+cdjrO8YpgjqoSM 1UC8vQgi7sAJojCP7YPcFVAS46uDPzlBi9GoSn3Lg6wJa3WYSjR2C6GAqbWybH/g 9DBCWbAUTGNq+ey8ieFkYTQz7hklZNJVepG9OuNKgxbhJ03gXHZxcYG0Pwej8yLE qQtCBhu6ok/fBx/eYpPXmOXdewml2Oq9mwJP54cuEUVOuKL5ekHanoQ0HSlPZ6IQ yBSSona1eoYZhluZ2NtOPz4c6hjRSpxzDDr+SpL7UzKlCDejhW7y7O4oSycZ6GNo QgSotxWJvY754MvGmDWWz17Z9TfjLZDiohm9z50I6pb5XORNeSqzcbl/Ls75TnaU //a/9UD3SlPfk86iwJd4EmR+nRU6uq4Z/Mg1DR5vNuPdgbaVzKFVZyk4NGs0GCL4 /VxNCw8liim8mQU2UXZqSjdvDaIzVA01YujYjd1agv9P+PNO+Xt5May8bWLT5CS7 PUCFsWZKUEU= =5sU4 -----END PGP SIGNATURE-----