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Posted on 14 October 2026
FreeBSD security notificat=============================================================================FreeBSD-SA-26:71.sound Security Advisory
The FreeBSD Project
Topic: TOCTOU race between sound(4) buffer resizing and mmap
Category: core
Module: sound
Announced: 2026-10-14
Credits: Hazley Samsudin of GovTech CSG
Affects: All supported versions of FreeBSD.
Corrected: 2026-10-14 16:02:57 UTC (stable/15, 15.1-STABLE)
2026-10-14 16:04:37 UTC (releng/15.1, 15.1-RELEASE-p5)
2026-10-14 16:03:13 UTC (stable/14, 14.5-STABLE)
2026-10-14 16:04:10 UTC (releng/14.5, 14.5-RELEASE-p2)
2026-10-14 16:03:54 UTC (releng/14.4, 14.4-RELEASE-p11)
CVE Name: CVE-2026-101308
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
FreeBSD provides audio support through the sound(4) driver, which
presents each audio device as a set of character device nodes such as
/dev/dsp.
Applications can map a channel buffer via mmap(2) for low-latency audio
I/O.
II. Problem Description
When an audio channel's buffer needs to be resized, the sound(4)
driver checks that the buffer is not memory-mapped and then drops the
channel lock to allocate a new buffer. An mmap(2) call on another
thread can complete during this window, after which the resize path
frees the now-mapped buffer without rechecking.
III. Impact
An unprivileged local user with access to a sound device can exploit
this race to trigger a use-after-free in the kernel, potentially
escalating privileges.
IV. Workaround
No workaround is available. Systems with no sound devices are
unaffected.
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.
[FreeBSD 15.x]
# fetch https://security.FreeBSD.org/patches/SA-26:71/sound-15.patch
# fetch https://security.FreeBSD.org/patches/SA-26:71/sound-15.patch.asc
# gpg --verify sound-15.patch.asc
[FreeBSD 14.x]
# fetch https://security.FreeBSD.org/patches/SA-26:71/sound-14.patch
# fetch https://security.FreeBSD.org/patches/SA-26:71/sound-14.patch.asc
# gpg --verify sound-14.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/ 07eacba075ab stable/15-n286005
releng/15.1/ 908bde55f070 releng/15.1-n283635
stable/14/ d3b8957e2a82 stable/14-n275352
releng/14.5/ 658b24eba235 releng/14.5-n274890
releng/14.4/ ea6ecd1e3762 releng/14.4-n273785
- -------------------------------------------------------------------------
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-2026-101308>
The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-26:71.sound.asc>
