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============================================================================= FreeBSD-SA-26:21.ptrace Security Advisory
The FreeBSD Project

Topic: Missing validation in ptrace(PT_SC_REMOTE)

Category: core
Module: ptrace
Announced: 2026-05-20
Credits: Yuxiang Yang, Yizhou Zhao, Ao Wang, Xuewei Feng, Qi Li,
and Ke Xu from Tsinghua University using GLM-5.1 from Z.ai Credits: Ryan at Calif.io
Affects: All supported versions of FreeBSD.
Corrected: 2026-05-20 19:36:40 UTC (stable/15, 15.0-STABLE)
2026-05-20 19:39:34 UTC (releng/15.0, 15.0-RELEASE-p9)
2026-05-20 19:37:59 UTC (stable/14, 14.4-STABLE)
2026-05-20 19:39:59 UTC (releng/14.4, 14.4-RELEASE-p5)
2026-05-20 19:40:37 UTC (releng/14.3, 14.3-RELEASE-p14)
CVE Name: CVE-2026-45253

This vulnerability was independently reported by multiple parties prior to publication.

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

The ptrace(2) system call provides facilities for a debugger to control the execution of a target process and to obtain status information about it.
Among other capabilities, it permits a debugger to execute arbitrary system calls in the target process via the PT_SC_REMOTE operation.

II. Problem Description

ptrace(PT_SC_REMOTE) failed to properly validate parameters for the syscall(2) and __syscall(2) meta-system calls. As a result, a user with the ability to debug a process may trigger arbitrary code execution in the kernel, even if
the target process has no special privileges.

III. Impact

The missing validation allows an unprivileged local user to escalate privileges, potentially gaining full control of the affected system.

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 15.0]
# fetch https://security.FreeBSD.org/patches/SA-26:21/ptrace-15.patch
# fetch https://security.FreeBSD.org/patches/SA-26:21/ptrace-15.patch.asc
# gpg --verify ptrace-15.patch.asc

[FreeBSD 14.4]
# fetch https://security.FreeBSD.org/patches/SA-26:21/ptrace-14.4.patch
# fetch https://security.FreeBSD.org/patches/SA-26:21/ptrace-14.4.patch.asc
# gpg --verify ptrace-14.4.patch.asc

[FreeBSD 14.3]
# fetch https://security.FreeBSD.org/patches/SA-26:21/ptrace-14.3.patch
# fetch https://security.FreeBSD.org/patches/SA-26:21/ptrace-14.3.patch.asc
# gpg --verify ptrace-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/ 3b4afab9add2 stable/15-n283643 releng/15.0/ fd24dd0b38a8 releng/15.0-n281043 stable/14/ fac902a3e039 stable/14-n274166 releng/14.4/ c21d23f0f8be releng/14.4-n273706 releng/14.3/ 45bd421661c4 releng/14.3-n271506
- -------------------------------------------------------------------------

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-2026-45253>

The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-26:21.ptrace.asc> -----BEGIN PGP SIGNATURE-----

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