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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
