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FreeBSD-SA-26:55.elf Security Advisory
The FreeBSD Project
Topic: Race condition in ELF core dump segment counting
Category: core
Module: elf
Announced: 2026-07-29
Credits: Maik Muench of Secfault Security
Affects: All supported versions of FreeBSD.
Corrected: 2026-07-29 17:48:45 UTC (stable/15, 15.1-STABLE)
2026-07-29 17:50:37 UTC (releng/15.1, 15.1-RELEASE-p2)
2026-07-29 17:50:11 UTC (releng/15.0, 15.0-RELEASE-p12)
2026-07-29 17:49:04 UTC (stable/14, 14.4-STABLE)
2026-07-29 17:49:38 UTC (releng/14.4, 14.4-RELEASE-p8)
CVE Name: CVE-2026-58088
For general information regarding FreeBSD Security Advisories, including
descriptions of the fields above, security branches, and the following
sections, please visit .
I. Background
When a process dumps core, the kernel writes an ELF file containing the
process's register state and memory contents. Each dumpable region of the
process's virtual memory map is represented by an ELF segment in the core
file.
II. Problem Description
The ELF core dump code counted the number of dumpable VM map entries,
allocated a buffer for the corresponding program headers, then iterated over
the map a second time to populate them. A process sharing the address space
via rfork(2) can mutate the map between the two passes, causing the second
pass to write program headers past the end of the buffer.
III. Impact
An unprivileged local user sharing an address space with a process that dumps
core can trigger an out-of-bounds write on the kernel heap, potentially
leading to privilege escalation.
IV. Workaround
Set sysctl kern.coredump=0 to disable core dumps entirely.
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-26:55/elf-15.patch
# fetch https://security.FreeBSD.org/patches/SA-26:55/elf-15.patch.asc
# gpg --verify elf-15.patch.asc
[FreeBSD 14.x]
# fetch https://security.FreeBSD.org/patches/SA-26:55/elf-14.patch
# fetch https://security.FreeBSD.org/patches/SA-26:55/elf-14.patch.asc
# gpg --verify elf-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/ 008d3bafa124 stable/15-n284648
releng/15.1/ 8592efddadf6 releng/15.1-n283595
releng/15.0/ 475a72f75478 releng/15.0-n281098
stable/14/ 89a88e4f2ddc stable/14-n274646
releng/14.4/ d46ec216104e releng/14.4-n273753
- -------------------------------------------------------------------------
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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