Actu
Vigil@nce: ncpfs, privilege elevation via ncpmount and ncpumount
February 2010 by Vigil@nce
SYNTHESIS OF THE VULNERABILITY
When the ncpmount and ncpumount tools are installed suid root, a
local attacker can use a symbolic link, in order to elevate his
privileges, to obtain information or to create a denial of service.
Severity: 2/4
Consequences: administrator access/rights, privileged
access/rights, user access/rights, data reading, denial of service
of service, denial of service of client
Provenance: user shell
Means of attack: 1 attack
Ability of attacker: technician (2/4)
Confidence: confirmed by the editor (5/5)
Diffusion of the vulnerable configuration: high (3/3)
Creation date: 29/01/2010
IMPACTED PRODUCTS
– Unix - plateform
DESCRIPTION OF THE VULNERABILITY
The ncpmount and ncpumount utilities are used to mount a remote
NCP (NetWare Core Protocol) share in a local directory. These
tools are frequently installed suid root.
However, the ncpmount tool does not atomically check the mount
directory. A local attacker can therefore:
– call ncpmount to mount a remote share on /home/user/mydir
– during its execution, replace /home/user/mydir by a symbolic link to /privatedirectory
– wait for ncpmount to mount the share on /privatedirectory
So, by modifying/reading the content of the share on the remote
server, the local attacker can modify/read to content of
/privatedirectory.
Moreover, the ncpumount tool does not atomically check the
directory to be unmounted. A local attacker can therefore:
– call "ncpumount /home/user/mydir"
– during its execution, replace /home/user/mydir by a symbolic
link to /privatedirectory
– wait for ncpumount to unmount /privatedirectory
A local attacker can thus unmount a mount point belonging to
another user.
When the ncpmount and ncpumount tools are installed suid root, a
local attacker can therefore use a symbolic link, in order to
elevate his privileges, to obtain information or to create a
denial of service.
CHARACTERISTICS
Identifiers: 532940, CVE-2009-3297, VIGILANCE-VUL-9392
http://vigilance.fr/vulnerability/ncpfs-privilege-elevation-via-ncpmount-and-ncpumount-9392
