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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2019.3955 FreeBSD -- IPv6 remote Denial-of-Service 25 October 2019 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: linux kernel Publisher: FreeBSD Operating System: FreeBSD UNIX variants (UNIX, Linux, OSX) Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2019-5611 Original Bulletin: https://www.freebsd.org/security/advisories/FreeBSD-SA-19:22.mbuf.asc Comment: This advisory references vulnerabilities in the Linux kernel that also affect distributions other than FreeBSD. It is recommended that administrators running Linux check for an updated version of the kernel for their system. - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-19:22.mbuf Security Advisory The FreeBSD Project Topic: IPv6 remote Denial-of-Service Category: kernel Module: net Announced: 2019-08-20 Credits: Clement Lecigne Affects: All supported versions of FreeBSD. Corrected: 2019-08-10 00:01:25 UTC (stable/12, 12.0-STABLE) 2019-08-20 17:49:33 UTC (releng/12.0, 12.0-RELEASE-p10) 2019-08-10 00:02:45 UTC (stable/11, 11.3-STABLE) 2019-08-20 17:49:33 UTC (releng/11.3, 11.3-RELEASE-p3) 2019-08-20 17:49:33 UTC (releng/11.2, 11.2-RELEASE-p14) CVE Name: CVE-2019-5611 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 mbufs are a unit of memory management mostly used in the kernel for network packets and socket buffers. m_pulldown(9) is a function to arrange the data in a chain of mbufs. II. Problem Description Due do a missing check in the code of m_pulldown(9) data returned may not be contiguous as requested by the caller. III. Impact Extra checks in the IPv6 code catch the error condition and trigger a kernel panic leading to a remote DoS (denial-of-service) attack with certain Ethernet interfaces. At this point it is unknown if any other than the IPv6 code paths can trigger a similar condition. IV. Workaround For the currently known attack vector systems with IPv6 not enabled are not vulnerable. On systems with IPv6 active, IPv6 fragmentation may be disabled, or a firewall can be used to filter out packets with certain or excessive amounts of extension headers in a first fragment. These rules may be dependent on the operational needs of each site. V. Solution Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date, and reboot. 1) 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 # shutdown -r +10min "Rebooting for security update" 2) 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. # fetch https://security.FreeBSD.org/patches/SA-19:22/mbuf.patch # fetch https://security.FreeBSD.org/patches/SA-19:22/mbuf.patch.asc # gpg --verify mbuf.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile your kernel as described in <URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - - ------------------------------------------------------------------------- stable/12/ r350828 releng/12.0/ r351259 stable/11/ r350829 releng/11.3/ r351259 releng/11.2/ r351259 - - ------------------------------------------------------------------------- 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://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238787> <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-5611> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:22.mbuf.asc> - -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAl1cPgFfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cK+4w/7BCGyLpeSCIaHMpKdZvSqKc6RptLyxPq1q6XO/5fUxQiBXuwxfZIUO45o VyQCsuVf0QDeT/HaMJAdTr450RlSs1ozyzEmd2iLfwqmpc8JRemihrzHkNMfny1U Y4ffN6zyrOLyFeyQcdbgHUKHwuAvGZFhR/PtPJfWDmULi0vW5PHBGjxOQmxKbbUr 6zcR+gKrm5E3vLW4vD2gvsB1RGyOzUBOaEeQU36LE1/W6hhgwtXAkZacEP+W4BiB jPbG7u23C3a2KcRImCWM2vJ5dZFoa0Mz5+vHzaSMwPT49KRRRRkcd7+azqUfbGg0 k9Py6KuwGhclNmehpUth0NlvR89JV58Fbkh7TaCWHV51hAWoH/1EQdJNY9yb0eAZ AgsvAiotWU1VNDcF2xWaf5m3VE87jl0/Bz9BgpVFI0kHuof4OwiG9PkdFI1q0Yl2 TdkksZj1iRETN8/Qt5HGzY1pGQFRc7b+nE9GIfIUcEH1B7d7Gb58DVElZ95Og+EF bGwR6/e7r39mBsqs0qloYgk/2c6B4vuFyt8b9Yhuw4ns0SpO4cP9XYXawUff7+p3 oLo7dqPKn8fMRLhT0/QZfPRyluUshVvJW1Yg9HWdYMYm7wFAilemnMWMxJKIUOmt pkQx3e6Tvk3VNkls4yv7GbApO5iMNXaBvC2JYMP0GUiQ1FOkB9M= =ip7/ - -----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: https://www.auscert.org.au/bulletins/ =========================================================================== 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). 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