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NSFOCUS Security Advisory(SA2003-08)

Topic: HP-UX libc NLSPATH Environment Variable Privilege Elevation Vulnerability

Release Date: 2003-11-13

CVE CAN ID: CAN-2003-0090

http://www.nsfocus.com/english/homepage/research/0308.htm

Affected system:
===================
- - HP-UX B.11.00
- - HP-UX B.11.11

Summary:
=========

NSFOCUS Security Team has found that the libc in HP-UX cannot restrict the
NLSPATH variable used by suid root program, which causes a format string 
vulnerability. Exploiting the vulnerability local attacker could gain root 
privilege.

Description:
============

Many programs in HP-UX use catopen()/catgets() and other functions in libc
to display localized information. When catopen() has detected the environment
variable NLSPATH, it will open the specified file and read messages from
it.

However, catopen() doesn't restrict the suid root program uses NLSPATH, which
allows local attackers to set NLSPATH variable and specify a locale file
crafted by themselves. When the suid root program uses catopen() to open the
message file and passes the data from it to *printf(), it might cause a format
string vulnerability.

Any suid root program that uses catopen()/catgets() maybe vulnerable. By exploiting
the vulnerability local attackers could gain root privilege.

According to the test, at least the following programs are vulnerable:

- -r-sr-xr-x   1 root       bin          45056 Nov 14  2000 /usr/bin/at
- -r-sr-xr-x   1 root       bin          24576 Nov 14  2000 /usr/bin/crontab
- -r-sr-xr-x   1 root       bin          45056 Nov 14  2000 /usr/bin/ct
- -r-sr-xr-x   1 root       bin          36864 Apr 19  2001 /usr/bin/cu
- -r-sr-xr-x   1 root       bin          20480 Nov 14  2000 /usr/lbin/exrecover
- -r-sr-xr-x   1 root       bin          40960 Aug 16  2001 /usr/bin/lp
- -r-sr-sr-x   2 root       mail         45056 Nov 14  2000 /usr/bin/mail
- -r-sr-xr-x   5 root       bin          45056 Nov 14  2000 /usr/bin/passwd
- -r-sr-xr-x   1 root       bin          24576 Nov 14  2000 /usr/bin/su
- -r-sr-xr-x  11 root       bin        1921024 Nov  6  2001 /usr/sbin/swinstall
- -r-sr-xr-x   2 root       bin        1028096 Nov  6  2001 /usr/sbin/swpackage

Workaround:
=============

NSFOCUS suggests to temporarily remove the suid root bit for all the
programs. However, it might brings about many inconvenience. You are suggested
to apply the appropriate patch at the earliest possibility.

Vendor Status:
==============

2002.11.19 Informed the vendor
2002.12.05 Vendor confirmed the vulnerability
2003.11.05 Vendor released a security bulletin (HPSBUX0311-294) and relative
            patches for the vulnerability.

Detailed information for the HP security bulletin is available at:
http://www1.itrc.hp.com/service/cki/docDisplay.do?docId=HPSBUX0311-294

Note: Valid ITRC account is required for the link above.

Patch ID:

HP-UX B.11.22 PHCO_29329
HP-UX B.11.11 PHCO_29495
HP-UX B.11.00 PHCO_29284
HP-UX B.10.20 PHCO_26158

Additional Information:
========================

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2003-0090 to this issue. This is a candidate for inclusion in the
CVE list (http://cve.mitre.org), which standardizes names for security
problems. Candidates may change significantly before they become official
CVE entries.

Acknowledgment
===============

Yang Jilong of NSFOCUS Security Team found the vulnerability.

DISCLAIMS:
==========
THE INFORMATION PROVIDED IS RELEASED BY NSFOCUS "AS IS" WITHOUT WARRANTY
OF ANY KIND. NSFOCUS DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED,
EXCEPT FOR THE WARRANTIES OF MERCHANTABILITY. IN NO EVENT SHALL NSFOCUS
BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT,
INCIDENTAL,CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES,
EVEN IF NSFOCUS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
DISTRIBUTION OR REPRODUCTION OF THE INFORMATION IS PROVIDED THAT THE
ADVISORY IS NOT MODIFIED IN ANY WAY.

Copyright 1999-2003 NSFOCUS. All Rights Reserved. Terms of use.


NSFOCUS Security Team <security@nsfocus.com>
NSFOCUS INFORMATION TECHNOLOGY CO.,LTD
(http://www.nsfocus.com)

PGP Key: http://www.nsfocus.com/homepage/research/pgpkey.asc
Key fingerprint = F8F2 F5D1 EF74 E08C 02FE 1B90 D7BF 7877 C6A6 aF6DA
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