Headline
CVE-2019-5606
In FreeBSD 12.0-STABLE before r349805, 12.0-RELEASE before 12.0-RELEASE-p8, 11.3-STABLE before r349806, 11.3-RELEASE before 11.3-RELEASE-p1, and 11.2-RELEASE before 11.2-RELEASE-p12, code which handles close of a descriptor created by posix_openpt fails to undo a signal configuration. This causes an incorrect signal to be raised leading to a write after free of kernel memory allowing a malicious user to gain root privileges or escape a jail.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-19:13.pts Security Advisory The FreeBSD Project Topic: pts(4) write-after-free Category: core Module: kernel Announced: 2019-07-24 Credits: syzkaller Affects: All supported versions of FreeBSD. Corrected: 2019-07-07 14:19:46 UTC (stable/12, 12.0-STABLE) 2019-07-24 12:53:06 UTC (releng/12.0, 12.0-RELEASE-p8) 2019-07-07 14:20:14 UTC (stable/11, 11.2-STABLE) 2019-07-24 12:53:06 UTC (releng/11.2, 11.2-RELEASE-p12) 2019-07-24 12:53:06 UTC (releng/11.3, 11.3-RELEASE-p1) CVE Name: CVE-2019-5606 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background The posix_openpt(2) system call allocates a pseudo-terminal device and returns a descriptor referencing that device. Such a descriptor may be configured such that a SIGIO signal will be sent to a designated process or process group when the device is ready to perform I/O. II. Problem Description The code which handles a close(2) of a descriptor created by posix_openpt(2) fails to undo the configuration which causes SIGIO to be raised. This bug can lead to a write-after-free of kernel memory. III. Impact The bug permits malicious code to trigger a write-after-free, which may be used to gain root privileges or escape a jail. IV. Workaround No workaround is available. V. Solution Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date. Perform one of the following: 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 “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-19:13/pts.patch # fetch https://security.FreeBSD.org/patches/SA-19:13/pts.patch.asc # gpg --verify pts.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 and reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/12/ r349805 releng/12.0/ r350282 stable/11/ r349806 releng/11.2/ r350282 releng/11.3/ r350282 - ------------------------------------------------------------------------- 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: VII. References The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAl04Wl9fFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cLZDA//SGC+7Vghtofm/CzylIXhC1drFOxNYJOF7KEJqDwsRR3U9S99Q9NBWS5+ e+/vJzvV0+epZNQXDlit5a76jGwy4fNuutNh0J3APHe/l0Zp/PhM56IwRWQgqAkQ hF67xhHxFZs8AH6/bw21N4IkRrAZHmrrCY8ubZArjoUi0gCoFzAYRw1Nh/JTQoLS IGuqUFaMZWKvu3aeJiikLjHiJUMRAY7sxh+iSBSp99dsLkASqQZtx1grmosljttN fuD7qO2f067EWUpC50JTbNt9V7za854hrlOp8jn1g51O4fWWJoEEL2/0VUeOO+fr aGS9UNal25NPr2zGzx2t0u1VNE3/YKoZ0tq+mQYtaXke32ZO15Ufby0YcLU4DF8d dU1ZoG2AGbWmBqgQ982hocq5Dn0r5yCHXDeEGguE1DsfyBuUEZw6zfYRtzIQ0swk wDrdETxpIMa8jaSGtDw2bilrLNRIVqYkXBJftC3fpXhlz6PyU6bZaFm00xrs7z1D EJMkuIWho9oMqLTU7bZNHv7JD4G3ziTF1h2tGXGcEKp02ImNZQnw3w5PBberFgto H4uJQCWgFqqddkjnSidX3Uj676LC99ERDEUlqi+xnXMmBScJnQuRtiUdbpOCkPD2 gLJmcyy7qjKw87i8KaQF5hUcym2D9xygbUV+I4RT93jR2DCVBA0= =Cpu+ -----END PGP SIGNATURE-----