FreeBSD Security Advisory FreeBSD-SA-26:57.unix

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-26:57.unix Security Advisory The FreeBSD Project Topic: Use-after-free in unix SOCK_STREAM message handling Category: core Module: unix Announced: 2026-08-25 Credits: Mark Johnston Affects: FreeBSD 15.0 and later Corrected: 2026-08-24 16:29:47 UTC (stable/15, 15.1-STABLE) 2026-08-25 16:01:22 UTC (releng/15.1, 15.1-RELEASE-p3) 2026-08-25 16:01:01 UTC (releng/15.0, 15.0-RELEASE-p13) CVE Name: CVE-2026-58090 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 provide a mechanism for processes on the same host to communicate. Processes can use unix domain sockets to exchange file descriptors, using the SCM_RIGHTS control message type. II. Problem Description The SOCK_STREAM receive path in the unix socket implementation failed to fully detach control messages from the socket buffer before processing them. Some error paths would free those messages, leaving freed data mbufs in the receive socket buffer. III. Impact An unprivileged local user can exploit this use-after-free to escalate privileges. 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, and reboot the system. Perform one of the following: 1) To update your vulnerable system installed from base system packages: Systems running a 15.0-RELEASE or later version of FreeBSD on the amd64 or arm64 platforms, which were installed using base system packages, can be updated via the pkg(8) utility: # pkg upgrade -r FreeBSD-base # shutdown -r +10min "Rebooting for a security update" 2) To update your vulnerable system installed from binary distribution sets: Systems running a RELEASE version of FreeBSD on the amd64 or arm64 platforms which were not installed using base system packages can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install # shutdown -r +10min "Rebooting for a 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. # fetch https://security.FreeBSD.org/patches/SA-26:57/unix.patch # fetch https://security.FreeBSD.org/patches/SA-26:57/unix.patch.asc # gpg --verify unix.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch -E -p0 < /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 This issue is corrected as of the corresponding Git commit hash in the following stable and release branches: Branch/path Hash Revision - ------------------------------------------------------------------------- stable/15/ 06833c3e9813 stable/15-n285079 releng/15.1/ 0e4c26a82cb1 releng/15.1-n283602 releng/15.0/ 21de91422ca2 releng/15.0-n281105 - ------------------------------------------------------------------------- Run the following command to see which files were modified by a particular commit: # git show --stat <commit hash> Or visit the following URL, replacing NNNNNN with the hash: <URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN> To determine the commit count in a working tree (for comparison against nNNNNNN in the table above), run: # git rev-list --count --first-parent HEAD VII. References <URL:https://www.cve.org/CVERecord?id=CVE-2026-58090> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-26:57.unix.asc> -----BEGIN PGP SIGNATURE----- iQJPBAEBCgA5FiEEthUnfoEIffdcgYM7bljekB8AGu8FAmqN3X0bFIAAAAAABAAO bWFudTIsMi41KzEuMTIsMCwzAAoJEG5Y3pAfABrvlAsP/1eqhZQS/YtepDbHml3h Cjuzc3eHFelAfDhMDaAn1/KJv6fUNHaJ3NQipdKL9hU78tXKIG287Ld3BpExBvp/ 7ODQiYENW94Nx07sm0HL9Qa0lznAQtUsniZ2mlua9+t00eYnEHd8qJkeL369IGhI qfpeIjbELLS6kkC8r6LVEI0ncDmeieXBcL20amwSASzWarw6HpWucF6zot/FOfUE S6hn8fLO+IQj+min9DzMGjNDq3r/dqDKXMXv68+En+5dhmO4HMOSibfTa1YdKfW4 SJziul0mOfaMWMCssd3b2HN5SHe9vx4vtf7TpBWfAvREbF3F95eelTzKrEkS+8Vx CvK6ApUukBG/866bATVri2bXnnnVuERXxi/1vMevd7dDcCZWrg/FKquoqzl/n1AD MM0U5PCn3PdCFJDNlNf8+ShYv9uFA6w7S2CJAkGW2oNdR9WKZcOHu4bwvxBod2hj xhk7xZ+hzv5Fb7ulf2bsi87BhDWrkOvRmCHh5oRKbGX/FrvUx3V1OCuFbnORxCJT g2MQOl7jBhhf0Gagy1bOIrqw/JH3m1Y2Lk6FgJLfNF6R1YJbWZg5oV3WIraUBr25 EruKOmOw4CTwL0hpUX2+wO1+/QaoW1JDb3GC7wSADRNNMCnTCtFJvNS+f+jcOchL usbogTLMhfpofgBignADKZsd =7aT1 -----END PGP SIGNATURE-----