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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2019.0347 File description reference count leak 6 February 2019 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: FreeBSD kernel Publisher: FreeBSD Operating System: FreeBSD Impact/Access: Root Compromise -- Existing Account Resolution: Patch/Upgrade CVE Names: CVE-2019-5596 Original Bulletin: https://security.freebsd.org/advisories/FreeBSD-SA-19:02.fd.asc - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-19:02.fd Security Advisory The FreeBSD Project Topic: File description reference count leak Category: core Module: unix Announced: 2019-02-05 Credits: Peter Holm Affects: FreeBSD 12.0 Corrected: 2019-02-05 17:56:22 UTC (stable/12, 12.0-STABLE) 2019-02-05 18:11:15 UTC (releng/12.0, 12.0-RELEASE-p3) 2019-02-05 17:57:30 UTC (stable/11, 11.2-STABLE) CVE Name: CVE-2019-5596 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 UNIX-domain sockets are used for inter-process communication. It is possible to use UNIX-domain sockets to transfer rights, encoded as file descriptors, to another process. II. Problem Description FreeBSD 12.0 attempts to handle the case where the receiving process does not provide a sufficiently large buffer for an incoming control message containing rights. In particular, to avoid leaking the corresponding descriptors into the receiving process' descriptor table, the kernel handles the truncation case by closing descriptors referenced by the discarded message. The code which performs this operation failed to release a reference obtained on the file corresponding to a received right. This bug can be used to cause the reference counter to wrap around and free the file structure. III. Impact A local user can exploit the bug to gain root privileges or escape from a jail. IV. Workaround No workaround is available. 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, and reboot. 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 # shutdown -r +30 "Rebooting for security update" 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-19:02/fd.patch # fetch https://security.FreeBSD.org/patches/SA-19:02/fd.patch.asc # gpg --verify fd.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/ r343785 releng/12.0/ r343790 stable/11/ r343786 - - ------------------------------------------------------------------------- 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://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-5596> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:02.fd.asc> - -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAlxZ1YFfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cK7+w/+JeFIVM0QQC1R4wJFmT3bBaRumxGCx5PN5Ufe7ub/ztwsKQKJeps1aiS3 fzw3Ck1K7+joeG+cNwZNihmAyEa2Hgk+FDhQBX531yrwF1jQ2A2oKGfkhs5e02Ng k16MV9pVlNP1zQ3wFVBjFCCvBuVJ0A8XTxALY7ivZlj2edgSH1eL4SaP1mrSD2Xu pR2amN7WkAaIqvATK0VkWjYp6kUXtI8CBtdP3hpKz88rpYoZfWxupqtghnxgjIqt iuTOhbemvYuBvB+ErbtU/6Z4ffoHt9Csrk2MM56/RZRwyHmtC4CFqtxClrUpOoa2 2OcEbR8cZyEardSES78UBjbTwlOTVd5F4o86Q1bKytHjI72ycB5yKZkyiHmdJCjs EhlaDC/rnHxdYGvBuiLqFcNU5tJiGawZZwyozCQz67dGD89QzKQurKEWQ1YJvMsW ZwwJRSHrllUyJQBdqV/R3Qoaz2koeE9633jtqHDdUYKCZAgeFdic/6u9r4Rx2Nj5 JpTZU01bwvxNZPf35WbI2L+JbygR40b3FYbZ3skBqZylp+EkPGPxGpHGAxdKWeOy rzGBukIuWnLy9pmJ574oTZymw8Psvu2DJL3Csngak1HkcA9mA5vjnDBvk9mvqTgo YCfCewlfFwVa/exSK3q5oI9hxse0KvQI4cH2+c2b7NDMS9+DpTY= =pr7t - -----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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