fuse 2.8.5 and earlier does not properly handle when /etc/mtab cannot be updated, which allows local users to unmount arbitrary directories via a symlink attack.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - fuse 2.8.5 and earlier does not properly handle when /etc/mtab cannot be updated, which allows local users     to unmount arbitrary directories via a symlink attack. (CVE-2011-0541)

Note that Nessus relies on the presence of the package as reported by the vendor.

Race conditions in fuse allowed unprivileged users to umount arbitrary mount points (CVE-2011-0541,CVE-2010-3879,CVE-2011-0543).

The remote Oracle Linux 6 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2011-1083 advisory.

    [2.8.3-3]
    - Bump the release since the bz was set to the wrong target

    [2.8.3-2]
    - Fix another umount race (bz# 673250, CVE-2010-3879)

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The following security issues were fixed in fuse :

  - FUSE allowed local users to create mtab entries with     arbitrary pathnames, and consequently unmount any     filesystem, via a symlink attack on the parent directory     of the mountpoint of a FUSE filesystem. (CVE-2010-3879)

  - Avoid mounting a directory including evaluation of     symlinks, which might have allowed local attackers to     mount filesystems anywhere in the system.
    (CVE-2011-0541)

  - Avoid symlink attacks on the mount point written in the     mtab file. (CVE-2011-0543)

The remote Redhat Enterprise Linux 6 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2011:1083 advisory.

    FUSE (Filesystem in Userspace) can implement a fully functional file system     in a user-space program. These packages provide the mount utility,     fusermount, the tool used to mount FUSE file systems.

    Multiple flaws were found in the way fusermount handled the mounting and     unmounting of directories when symbolic links were present. A local user in     the fuse group could use these flaws to unmount file systems, which they     would otherwise not be able to unmount and that were not mounted using     FUSE, via a symbolic link attack. (CVE-2010-3879, CVE-2011-0541,     CVE-2011-0542, CVE-2011-0543)

    Note: The util-linux-ng RHBA-2011:0699 update must also be installed to     fully correct the above flaws.

    All users should upgrade to these updated packages, which contain     backported patches to correct these issues.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The following security issues were fixed in fuse and util-linux :

  - FUSE allowed local users to create mtab entries with     arbitrary pathnames, and consequently unmount any     filesystem, via a symlink attack on the parent directory     of the mountpoint of a FUSE filesystem. (CVE-2010-3879)

  - Avoid mounting a directory including evaluation of     symlinks, which might have allowed local attackers to     mount filesystems anywhere in the system.
    (CVE-2011-0541)

  - Avoid symlink attacks on the mount point written in the     mtab file. (CVE-2011-0543)

Additional two bugs were fixed in util-linux :

  - fixed retrying nfs mounts on rpc timeouts

  - allow seperate control of the internet protocol uses by     rpc.mount seperately of the protocol used by nfs.

New features were implemented: - mount now has --fake and
--no-canonicalize options, required for the symlink security fixes.
These were backported from mainline.

The following security issues were fixed :

  - FUSE allowed local users to create mtab entries with     arbitrary pathnames, and consequently unmount any     filesystem, via a symlink attack on the parent directory     of the mountpoint of a FUSE filesystem. (CVE-2010-3879)

  - Avoid mounting a directory including evaluation of     symlinks, which might have allowed local attackers to     mount filesystems anywhere in the system.
    (CVE-2011-0541)

  - Avoid symlink attacks on the mount point written in the     mtab file. Four bugs were fixed:. (CVE-2011-0543)

  - fixed retrying nfs mounts on rpc timeouts

  - allow seperate control of the internet protocol uses by     rpc.mount seperately of the protocol used by nfs.

  - Fixed locking in libuuid/uuid to avoid duplicate uuids.

  - mkswap bad block check marked every block bad in O(n!)     time on a good device New features were implemented :

  - mount now has --fake and --no-canonicalize options,     required for the symlink security fixes. These were     backported from mainline.

  - mount can now auto-detect and differentiate between     squashfs3 and squashfs (v4) filesystems, allowing     backward compatibility to the SUSE Linux Enterprise 11     GA codebase.

It was discovered that FUSE would incorrectly follow symlinks when checking mountpoints under certain conditions. A local attacker, with access to use FUSE, could unmount arbitrary locations, leading to a denial of service.

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Type	Severity
217323	Linux Distros Unpatched Vulnerability : CVE-2011-0541	Nessus	Misc.	Local	high
75508	openSUSE Security Update : fuse (openSUSE-SU-2011:0264-1)	Nessus	SuSE Local Security Checks	Local	medium
68309	Oracle Linux 6 : fuse (ELSA-2011-1083)	Nessus	Oracle Linux Local Security Checks	Local	high
57257	SuSE 10 Security Update : fuse (ZYPP Patch Number 7418)	Nessus	SuSE Local Security Checks	Local	medium
55635	RHEL 6 : fuse (RHSA-2011:1083)	Nessus	Red Hat Local Security Checks	Local	high
53724	openSUSE Security Update : fuse (openSUSE-SU-2011:0265-1)	Nessus	SuSE Local Security Checks	Local	medium
53256	SuSE 10 Security Update : FUSE (ZYPP Patch Number 7362)	Nessus	SuSE Local Security Checks	Local	medium
53231	SuSE 11.1 Security Update : FUSE (SAT Patch Number 4095)	Nessus	SuSE Local Security Checks	Local	medium
52479	Ubuntu 8.04 LTS / 9.10 / 10.04 LTS / 10.10 : fuse vulnerabilities (USN-1077-1)	Nessus	Ubuntu Local Security Checks	Local	low

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CVE-2011-0541

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