[Full-disclosure] [ GLSA 200511-17 ] FUSE: mtab corruption through fusermount

[Thierry Carrez]

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Gentoo Linux Security Advisory                           GLSA 200511-17
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                                            http://security.gentoo.org/
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  Severity: Normal
     Title: FUSE: mtab corruption through fusermount
      Date: November 22, 2005
      Bugs: #112902
        ID: 200511-17

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Synopsis
========

The fusermount utility from FUSE can be abused to corrupt the /etc/mtab
file contents, potentially allowing a local attacker to set
unauthorized mount options.

Background
==========

FUSE (Filesystem in Userspace) allows implementation of a fully
functional filesystem in a userspace program. The fusermount utility is
used to mount/unmount FUSE file systems.

Affected packages
=================

    -------------------------------------------------------------------
     Package      /  Vulnerable  /                          Unaffected
    -------------------------------------------------------------------
  1  sys-fs/fuse     < 2.4.1-r1                            >= 2.4.1-r1

Description
===========

Thomas Biege discovered that fusermount fails to securely handle
special characters specified in mount points.

Impact
======

A local attacker could corrupt the contents of the /etc/mtab file by
mounting over a maliciously-named directory using fusermount,
potentially allowing the attacker to set unauthorized mount options.
This is possible only if fusermount is installed setuid root, which is
the default in Gentoo.

Workaround
==========

There is no known workaround at this time.

Resolution
==========

All FUSE users should upgrade to the latest version:

    # emerge --sync
    # emerge --ask --oneshot --verbose ">=sys-fs/fuse-2.4.1-r1"

References
==========

  [ 1 ] CVE-2005-3531
        http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-3531

Availability
============

This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

  http://security.gentoo.org/glsa/glsa-200511-17.xml

Concerns?
=========

Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users machines is of utmost
importance to us. Any security concerns should be addressed to
security at gentoo.org or alternatively, you may file a bug at
http://bugs.gentoo.org.

License
=======

Copyright 2005 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

http://creativecommons.org/licenses/by-sa/2.0

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