GLSA 201603-04: FUSE: incorrect filtering of environment variables leading to privilege escalation

http://security.gentoo.org/

Severity:	normal
Title:	FUSE: incorrect filtering of environment variables leading to privilege escalation
Date:	03/09/2016
Bugs:	#550152
ID:	201603-04

Synopsis

The fusermount binary in FUSE does not properly clear the environment before invoking mount or umount as root that allows a local user to overwrite arbitrary files.

Background

FUSE provides an interface for filesystems implemented in userspace.

Affected packages

Package	Vulnerable	Unaffected	Architecture(s)
sys-fs/fuse	< 2.9.4	>= 2.9.4	All supported architectures

Description

The fusermount binary calls setuid(geteuid()) to reset the RUID when it invokes /bin/mount so that it can use privileged mount options that are normally restricted if RUID != EUID. FUSE does not properly clear environment variables before invoking mount or umount as root allowing this to be passed to operations using elevated privileges such as LIBMOUNT_MTAB that is used by the mount commands debugging feature.

Impact

The FUSE vulnerability allows a local, unprivileged user to overwrite arbitrary files on the system.

Workaround

There is no known work around at this time.

Resolution

All FUSE users should upgrade to the latest version:

      # emerge --sync
      # emerge --ask --oneshot --verbose ">=sys-fs/fuse-2.9.4"

References

CVE-2015-3202

Availability

This GLSA and any updates to it are available for viewing at the Gentoo Security Website: http://security.gentoo.org/glsa/glsa-201603-04.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@gentoo.org or alternatively, you may file a bug at https://bugs.gentoo.org.