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============================================================================= FreeBSD-SA-26:17.libnv Security Advisory
The FreeBSD Project

Topic: Heap overflow in libnv

Category: core
Module: libnv
Announced: 2026-04-29
Credits: Mariusz Zaborski
Affects: All supported versions of FreeBSD.
Corrected: 2026-04-29 14:47:52 UTC (stable/15, 15.0-STABLE)
2026-04-29 14:48:33 UTC (releng/15.0, 15.0-RELEASE-p7)
2026-04-29 14:48:57 UTC (stable/14, 14.4-STABLE)
2026-04-29 14:49:48 UTC (releng/14.4, 14.4-RELEASE-p3)
2026-04-29 14:49:28 UTC (releng/14.3, 14.3-RELEASE-p12)
2026-04-29 14:50:10 UTC (stable/13, 13.5-STABLE)
2026-04-29 14:50:22 UTC (releng/13.5, 13.5-RELEASE-p13)
CVE Name: CVE-2026-35547

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

libnv is a general-purpose library designed for storing and exchanging sets
of name-value pairs. This library can serve as an Inter-Process
Communication (IPC) framework, enabling processes to exchange data and file descriptors. For example, it is used in libcasper to establish communication between privileged and unprivileged processes. Additionally, libnv can function as an interface for communication between userland and kernel.

Originally, libnv was inspired by OpenZFS' nvlist implementation. However,
the implementations are separate. This advisory relates only to the base system implementation of libnv, not the one in OpenZFS.

II. Problem Description

When processing the header of an incoming message, libnv failed to properly validate the message size.

III. Impact

The lack of validation allows a malicious program to write outside the bounds of a heap allocation. This can trigger a crash or system panic, and it may
be possible for an unprivileged user to exploit the bug to elevate their 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.

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, or the i386 platform on FreeBSD 13, 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.

# fetch https://security.FreeBSD.org/patches/SA-26:17/libnv.patch
# fetch https://security.FreeBSD.org/patches/SA-26:17/libnv.patch.asc
# gpg --verify libnv.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/ 414e25d7d512 stable/15-n283381 releng/15.0/ b345e07c8d71 releng/15.0-n281033 stable/14/ 1cbd6e148249 stable/14-n274082 releng/14.4/ 4f0992ce23b0 releng/14.4-n273697 releng/14.3/ aa15809f85de releng/14.3-n271497 stable/13/ 05b91c2a7106 stable/13-n259863 releng/13.5/ f7f48005fbe2 releng/13.5-n259219
- -------------------------------------------------------------------------

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-2026-35547>

The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-26:17.libnv.asc> -----BEGIN PGP SIGNATURE-----

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