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Posted on 10 June 2026
FreeBSD security notificat=============================================================================FreeBSD-SA-26:32.elf Security Advisory
The FreeBSD Project
Topic: ASLR bypass for setuid executables via procctl(2)
Category: core
Module: kernel
Announced: 2026-06-09
Credits: Synacktiv
Affects: All supported versions of FreeBSD
Corrected: 2026-06-09 19:17:35 UTC (stable/15, 15.1-STABLE)
2026-06-09 19:20:13 UTC (releng/15.1, 15.1-RC3-p1)
2026-06-09 19:19:51 UTC (releng/15.0, 15.0-RELEASE-p10)
2026-06-09 19:17:53 UTC (stable/14, 14.4-STABLE)
2026-06-09 19:19:13 UTC (releng/14.4, 14.4-RELEASE-p6)
2026-06-09 19:18:43 UTC (releng/14.3, 14.3-RELEASE-p15)
CVE Name: CVE-2026-49414
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
Address Space Layout Randomization (ASLR) randomizes the base addresses
of executable images and shared libraries in a process's address space.
FreeBSD enables ASLR by default for Position-Independent Executables
(PIEs).
The procctl(2) system call allows a process to set per-process ASLR
preferences, including force-disabling randomization. When a setuid or
setgid binary is executed, the kernel is expected to ignore any such
user-set preferences if they come from an unprivileged user.
II. Problem Description
The ELF image activator cleared per-process ASLR preference flags for
setuid binaries after the code that computes the PIE base address,
rather than before. As a result, a user-requested ASLR disable was
still in effect at the point where the base address was chosen.
III. Impact
An unprivileged local user can disable ASLR for a setuid PIE binary by
calling procctl(2) before execve(2). This makes exploitation of any
separate memory corruption vulnerability in that binary significantly
easier.
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 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-26:32/elf-15.patch
# fetch https://security.FreeBSD.org/patches/SA-26:32/elf-15.patch.asc
# gpg --verify elf-15.patch.asc
[FreeBSD 14.4]
# fetch https://security.FreeBSD.org/patches/SA-26:32/elf-14.4.patch
# fetch https://security.FreeBSD.org/patches/SA-26:32/elf-14.4.patch.asc
# gpg --verify elf-14.4.patch.asc
[FreeBSD 14.3]
# fetch https://security.FreeBSD.org/patches/SA-26:32/elf-14.3.patch
# fetch https://security.FreeBSD.org/patches/SA-26:32/elf-14.3.patch.asc
# gpg --verify elf-14.3.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
This issue is corrected as of the corresponding Git commit hash in the
following stable and release branches:
Branch/path Hash Revision
- -------------------------------------------------------------------------
stable/15/ e1cdc49846c1 stable/15-n283888
releng/15.1/ 796579bcfbc4 releng/15.1-n283557
releng/15.0/ 6e51dfc401e7 releng/15.0-n281059
stable/14/ e417948e6139 stable/14-n274317
releng/14.4/ 547fc2a98a24 releng/14.4-n273721
releng/14.3/ 744f62ccbf82 releng/14.3-n271521
- -------------------------------------------------------------------------
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-2026-49414>
The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-26:32.elf.asc>
