FreeBSD Security Advisory FreeBSD-SA-13:08.nfsserver

Type securityvulns
Reporter Securityvulns
Modified 2013-07-29T00:00:00



============================================================================= FreeBSD-SA-13:08.nfsserver Security Advisory The FreeBSD Project

Topic: Incorrect privilege validation in the NFS server

Category: core Module: nfsserver Announced: 2013-07-26 Credits: Rick Macklem, Christopher Key, Tim Zingelman Affects: FreeBSD 8.3, FreeBSD 9.0 and FreeBSD 9.1 Corrected: 2012-12-28 14:06:49 UTC (stable/9, 9.2-BETA2) 2013-07-26 22:40:23 UTC (releng/9.1, 9.1-RELEASE-p5) 2013-01-06 01:11:45 UTC (stable/8, 8.3-STABLE) 2013-07-26 22:40:29 UTC (releng/8.3, 8.3-RELEASE-p9) CVE Name: CVE-2013-4851

For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:>.

I. Background

The Network File System (NFS) allows a host to export some or all of its file systems so that other hosts can access them over the network and mount them as if they were on local disks. FreeBSD includes both server and client implementations of NFS.

II. Problem Description

The kernel incorrectly uses client supplied credentials instead of the one configured in exports(5) when filling out the anonymous credential for a NFS export, when -network or -host restrictions are used at the same time.

III. Impact

The remote client may supply privileged credentials (e.g. the root user) when accessing a file under the NFS share, which will bypass the normal access checks.

IV. Workaround

Systems that do not provide the NFS service are not vulnerable. Systems that do provide the NFS service are only vulnerable when -mapall or -maproot is used in combination with network and/or host restrictions.

V. Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date.

2) 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.



gpg --verify nfsserver.patch.asc

b) Apply the patch.

cd /usr/src

patch < /path/to/patch

c) Recompile your kernel as described in <URL:> and reboot the system.

3) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64 platforms can be updated via the freebsd-update(8) utility:

freebsd-update fetch

freebsd-update install

VI. Correction details

The following list contains the correction revision numbers for each affected branch.

Branch/path Revision

stable/8/ r245086 releng/8.3/ r253694 stable/9/ r244772 releng/9.1/ r253693

To see which files were modified by a particular revision, run the following command, replacing XXXXXX with the revision number, on a machine with Subversion installed:

svn diff -cXXXXXX --summarize svn://

Or visit the following URL, replacing XXXXXX with the revision number:


VII. References


The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE-----

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