[Full-disclosure] iDefense Security Advisory 04.12.07: Hewlett Packard HP-UX Remote pfs_mountd.rpc Buffer Overflow Vulnerability

Hewlett Packard HP-UX Remote pfs_mountd.rpc Buffer Overflow Vulnerability

iDefense Security Advisory 04.12.07
Apr 12, 2007


PFS (the Portable File System) allows mounting of ISO 9660, High Sierra,
and Rock Ridge (ISO 9660 with Rock Ridge extensions) CD-ROM disks. The
daemon pfs_mountd.rpc is an RPC extension that is launched along with
pfsd in order to allow the easy mounting of these file systems under
HP-UX. It is remotely accessible over TCP and UDP.


Remote exploitation of a buffer overflow vulnerability in pfs_mountd.rpc
included in multiple versions of Hewlett Packard Co. HP-UX allows for
remote root access.

If a remote user sends two specially crafted packets over UDP, the
buffer overflow is triggered. One must first send a call to procedure
5, and soon thereafter send the actual payload to procedure 2. Due to
the closed nature of the pfs_mountd.rpc protocol specification, it is
unclear at this time what functions the respective procedures actually


The seriousness of this vulnerability is reduced by the fact that in
most cases an attacker will only have one chance at exploitation until
an administrator restarts the crashed daemon after a failed attempt.
However, the attack is functional over UDP, thus allowing an attacker
to completely spoof the attack, possibly even making it appear from
inside a trusted network.


iDefense has confirmed the existence of this vulnerability in HP-UX
11.11i. It is suspected that previous versions are also vulnerable.


Adding firewall rules may not be enough to stop this attack due to the
fact that it can be spoofed.


Hewlett-Packard discontinued support for the PFS on March 1st, 2004. As
a solution to this vulnerability, Hewlett-Packard recommends
discontinuing the use of PFS. More information is available from HP
Security Bulletin HPSBUX02203 at the following URL.



A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.


10/25/2004 Initial vendor notification
10/25/2004 Initial vendor response
12/19/2005 Second vendor notification
01/30/2007 Third vendor notification
04/12/2007 Coordinated public disclosure


This vulnerability was discovered by iDefense Labs.

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