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FreeBSD-SA-26:37.vm Security Advisory
The FreeBSD Project
Topic: Use-after-free in device pager page list
Category: core
Module: vm
Announced: 2026-06-30
Credits: slidybat
Affects: All supported versions of FreeBSD.
Corrected: 2026-06-30 17:20:07 UTC (stable/15, 15.1-STABLE)
2026-06-30 17:21:52 UTC (releng/15.1, 15.1-RELEASE-p1)
2026-06-30 17:21:20 UTC (releng/15.0, 15.0-RELEASE-p11)
2026-06-30 17:19:47 UTC (stable/14, 14.4-STABLE)
2026-06-30 17:20:54 UTC (releng/14.4, 14.4-RELEASE-p7)
2026-06-30 17:20:27 UTC (releng/14.3, 14.3-RELEASE-p16)
CVE Name: CVE-2026-49418
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit .
I. Background
The FreeBSD virtual memory subsystem uses pager objects to manage
memory-mapped device pages. Unmanaged device pager objects maintain
an internal list of pages allocated by the device fault handler; this
list is used to free the pages when the mapping is destroyed.
II. Problem Description
When msync(MS_INVALIDATE) is called on a mapping of an unmanaged device
object, the physical pages in the mapping range are marked invalid but
remain in the pager's page list. A subsequent page fault will cause the
fault handler to re-insert the page into the object's list. This
corrupts the list, and on object destruction the page is freed twice.
III. Impact
An unprivileged local user with access to a device that provides
memory-mapped I/O can trigger a use-after-free in the kernel, though
this is limited to a pool of objects ("fictitious pages") that are never
recycled for a different purpose. It may be possible to exploit this 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.
[FreeBSD 15.x]
# fetch https://security.FreeBSD.org/patches/SA-26:37/vm-15.patch
# fetch https://security.FreeBSD.org/patches/SA-26:37/vm-15.patch.asc
# gpg --verify vm-15.patch.asc
[FreeBSD 14.x]
# fetch https://security.FreeBSD.org/patches/SA-26:37/vm-14.patch
# fetch https://security.FreeBSD.org/patches/SA-26:37/vm-14.patch.asc
# gpg --verify vm-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
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/ 21929fbe1ced stable/15-n284323
releng/15.1/ 958de92ab2dc releng/15.1-n283565
releng/15.0/ 2baf56862bfd releng/15.0-n281067
stable/14/ 715831359fa7 stable/14-n274447
releng/14.4/ 4c9e89c85d7c releng/14.4-n273728
releng/14.3/ 78bd098b9f83 releng/14.3-n271528
- -------------------------------------------------------------------------
Run the following command to see which files were modified by a
particular commit:
# git show --stat
Or visit the following URL, replacing NNNNNN with the hash:
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
The latest revision of this advisory is available at
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