Vigil@nce: Samba, privilege elevation via mount.cifs
February 2010 by Vigil@nce
SYNTHESIS OF THE VULNERABILITY
When the mount.cifs tool is installed suid root, a local attacker
can use a symbolic link, in order to elevate his privileges or to
obtain information.
Severity: 2/4
Consequences: administrator access/rights, privileged
access/rights, user access/rights, data reading
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
– Samba
DESCRIPTION OF THE VULNERABILITY
The mount.cifs utility of the Samba suite is used to mount a
remote CIFS/SMB share in a local directory. This tool is
frequently installed suid root.
However, this tool does not atomically check the mount directory.
A local attacker can therefore:
– call mount.cifs to mount a remote share on /home/user/mydir
– during its execution, replace /home/user/mydir by a symbolic
link to /privatedirectory
– wait for mount.cifs 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.
When the mount.cifs tool is installed suid root, a local attacker
can therefore use a symbolic link, in order to elevate his
privileges or to obtain information.
CHARACTERISTICS
Identifiers: 532940, 6853, BID-37992, CVE-2009-3297,
VIGILANCE-VUL-9390
http://vigilance.fr/vulnerability/Samba-privilege-elevation-via-mount-cifs-9390