30.3 Third-Party Vulnerabilities and Security Advisories

FreeBSD uses pkg audit to query the vulnerability database (VuXML), providing CVE alerts for installed third-party software packages. This section introduces the audit command usage and explains the standard format of Security Advisories.

Monitoring Third-Party Security Issues

pkg polls a security issue database maintained by the FreeBSD security team and ports developers. This database can be kept automatically up-to-date through the periodic configuration file.

Specifically, the database references data from https://www.vuxml.org/freebsd/index.html by default.

Heavy use of third-party tools increases the risk of system intrusion. To audit third-party tools in Ports, administrators can update the database and check for known vulnerabilities in installed packages:

$ pkg audit -F

The output should resemble the following:

vulnxml file up-to-date
chromium-116.0.5845.96_1 is vulnerable:
  chromium -- multiple vulnerabilities
  CVE: CVE-2023-4431
  CVE: CVE-2023-4427
  CVE: CVE-2023-4428
  CVE: CVE-2023-4429
  CVE: CVE-2023-4430
  WWW: https://vuxml.FreeBSD.org/freebsd/5fa332b9-4269-11ee-8290-a8a1599412c6.html

samba413-4.13.17_5 is vulnerable:
  samba -- multiple vulnerabilities
  CVE: CVE-2023-3347
  CVE: CVE-2023-34966
  CVE: CVE-2023-34968
  CVE: CVE-2022-2127
  CVE: CVE-2023-34967
  WWW: https://vuxml.FreeBSD.org/freebsd/441e1e1a-27a5-11ee-a156-080027f5fec9.html

2 problem(s) in 2 installed package(s) found.

When there are no vulnerabilities, or no third-party software is installed, the output resembles the following:

Fetching vuln.xml.xz: 100%  1199 KiB   1.2 MB/s    00:01
vulnxml file up-to-date
0 problem(s) in 0 package(s) found.

By opening the displayed URL in a browser, administrators can obtain more information about the vulnerability.

This information includes the affected versions (by FreeBSD port version) and possibly other websites with relevant security advisories.

Security Advisories

The FreeBSD Project has a security team responsible for determining the end-of-life (EoL) dates for each FreeBSD version and providing security updates for supported versions that have not yet reached EoL. For more information, see the FreeBSD security page.

One of the responsibilities of the security team is to respond to reported security vulnerabilities in the FreeBSD operating system. Once a vulnerability is confirmed, the security team verifies the steps required for the fix and commits the fix to the source code, then publishes the details as a "Security Advisory." Security advisories are published on the FreeBSD website and mailed to the FreeBSD security notifications mailing list, the FreeBSD security mailing list, and the FreeBSD announcements mailing list.

Format of Security Advisories

The following is an example of a FreeBSD security advisory from https://www.freebsd.org/security/advisories/FreeBSD-SA-26:08.rpcsec_gss.asc, reporting CVE-2026-4747 Remote code execution via RPCSEC_GSS packet validation:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

=============================================================================
FreeBSD-SA-26:08.rpcsec_gss                                 Security Advisory
                                                          The FreeBSD Project

Topic:          Remote code execution via RPCSEC_GSS packet validation

Category:       core
Module:         rpcsec_gss
Announced:      2026-03-26
Credits:        Nicholas Carlini using Claude, Anthropic
Affects:        All supported versions of FreeBSD.
Corrected:      2026-03-26 01:25:23 UTC (stable/15, 15.0-STABLE)
                2026-03-26 01:11:20 UTC (releng/15.0, 15.0-RELEASE-p5)
                2026-03-26 01:28:47 UTC (stable/14, 14.4-STABLE)
                2026-03-26 01:14:55 UTC (releng/14.4, 14.4-RELEASE-p1)
                2026-03-26 01:16:01 UTC (releng/14.3, 14.3-RELEASE-p10)
                2026-03-26 01:30:12 UTC (stable/13, 13.5-STABLE)
                2026-03-26 01:34:10 UTC (releng/13.5, 13.5-RELEASE-p11)
CVE Name:       CVE-2026-4747

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

Generic Security Services (GSS) is an API which lets applications establish a
private, authenticated communication channel with a server, such as an NFS server.

RPCSEC_GSS is a module which enables the use of GSS with Sun RPC (rpc(3))
servers.  It is implemented in the kernel by the kgssapi.ko kernel module, and
used by the NFS server to enable Kerberos-based authentication and encryption
of traffic between the server and clients.  In userspace it is implemented by
the librpcsec_gss library.

II.  Problem Description

Each RPCSEC_GSS data packet is validated by a routine which checks a signature
in the packet.  This routine copies a portion of the packet into a stack buffer,
but fails to ensure that the buffer is sufficiently large, and a malicious
client can trigger a stack overflow.  Notably, this does not require the client
to authenticate itself first.

III. Impact

As kgssapi.ko's RPCSEC_GSS implementation is vulnerable, remote code execution
in the kernel is possible by an authenticated user that is able to send packets
to the kernel's NFS server while kgssapi.ko is loaded into the kernel.

In userspace, applications which have librpcgss_sec loaded and run an RPC server
are vulnerable to remote code execution from any client able to send it packets.
We are not aware of any such applications in the FreeBSD base system.

IV.  Workaround

No workaround is available.  Kernels that do not have kgssapi.ko loaded are not
vulnerable.  In userspace, any daemon linked with librpcgss_sec and running an
RPC server is vulnerable.

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-26:08/rpcsec_gss.patch
# fetch https://security.FreeBSD.org/patches/SA-26:08/rpcsec_gss.patch.asc
# gpg --verify rpcsec_gss.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel and the operating system as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and
<URL:https://www.FreeBSD.org/handbook/makeworld.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/                              1b00fdc1f3cd    stable/15-n282700
releng/15.0/                            4ec1b6213463  releng/15.0-n281013
stable/14/                              e5ed09ffd592    stable/14-n273840
releng/14.4/                            7ea03a4238e8  releng/14.4-n273677
releng/14.3/                            b6ce88ab9a5f  releng/14.3-n271477
stable/13/                              99ec7f9b9e48    stable/13-n259823
releng/13.5/                            c4f53a1adbd4  releng/13.5-n259207
- -------------------------------------------------------------------------

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-2026-4747>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-26:08.rpcsec_gss.asc>
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Each security advisory follows this format:

• Each security advisory is signed with the Security Officer's PGP key. The Security Officer's public key can be verified at OpenPGP Keys.
• The security advisory name always begins with FreeBSD-SA- (denoting FreeBSD Security Advisory), followed by a two-digit year (e.g., 26 for 2026, followed by a colon), the advisory sequence number for that year (08. being the 8th), and then the name of the affected application or subsystem (rpcsec_gss).

Field	Description
Topic	Summarizes the vulnerability
Category	Indicates the affected part of the system, which can be core, contrib, or ports. core indicates the vulnerability affects a core component of the FreeBSD operating system; contrib indicates it affects software shipped with FreeBSD (such as BIND); ports indicates it affects software available through the Ports Collection
Module	Indicates the component location. In this example, the rpcsec_gss module is affected, so the vulnerability affects an application installed with the operating system
Announced	The date the security advisory was published, indicating that the security team has verified the issue exists and the fix has been committed to the FreeBSD source repository
Credits	Acknowledges the individuals or organizations who discovered and reported the vulnerability
Affects	Indicates which FreeBSD versions are affected by this vulnerability
Corrected	Indicates the date, time, timezone, and version when the correction was made. The branches and their version numbers that have the fix merged are shown in parentheses. The version identifier includes the version number and, where applicable, the patch level — the letter p followed by a number indicates the patch sequence number, allowing users to track applied patches
CVE Name	Lists the advisory number in the public CVE database (if one exists)
Background	Provides a description of the affected module
Problem Description	Explains the vulnerability, potentially including information about the code defect and how it could be maliciously exploited
Impact	Describes the potential impact of the issue on the system
Workaround	Indicates whether a workaround exists for systems that cannot be immediately patched
Solution	Provides instructions for patching the affected system, a method that has been step-by-step tested and verified to ensure the system operates securely after patching
Correction Details	Lists the affected Git branches and the revision numbers containing the corrected code
References	Provides additional sources of information about the vulnerability

Exercises

1. Run pkg audit -F to obtain a list of all installed packages with known vulnerabilities, select a high-severity vulnerability from the list, and look up its detailed information in the CVE database.
2. Review all security advisories (FreeBSD-SA) published on the official FreeBSD website and create a histogram showing the year and the number of advisories.
3. In a test environment, downgrade a software package to an older version with a known vulnerability, run pkg audit to verify the vulnerability detection result, then fix the vulnerability and run the detection again, documenting the complete process.