iDEFENSE Security Advisory 02.10.03: Buffer Overflow In NOD32 Antivirus Software for Unix

["iDEFENSE Labs" <labs () idefense com>]

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iDEFENSE Security Advisory 02.10.03:
http://www.idefense.com/advisory/02.10.03.txt
Buffer Overflow In NOD32 Antivirus Software for Unix
February 10, 2003

I. BACKGROUND

Eset Software's NOD32 Antivirus System is a cross-platform anti-virus
application.  The Linux, FreeBSD, OpenBSD and NetBSD versions are compiled
from the same sources, which the vendor refers to as "nod32 for UNIX". 
More information is available at http://www.nod32.com/products/unix.htm .


II. DESCRIPTION

Local exploitation of a buffer overflow in NOD32 for UNIX could allow
attackers to gain super-user (root) privileges. The overflow occurs when
NOD32 parses a path with a name of length greater than 500 characters
(/tmp/AAAAA....AAA). An attacker can overwrite the first three bytes of
the eax and ecx registers, as can be seen from the following GDB output:

...
Program received signal SIGSEGV, Segmentation fault.
0x4207fa78 in strcmp () from /lib/i686/libc.so.6
(gdb) bt
#0 0x4207fa78 in strcmp () from /lib/i686/libc.so.6
#1 0x0804c2ba in scan_dir ()
#2 0x41414141 in ?? ()
Cannot access memory at address 0x41414141
(gdb) info registers
eax 0x4141414c 1094795596
ecx 0x4141414c 1094795596
... 


III. ANALYSIS

Exploitation allows local code execution with the privileges of the user
who spawned NOD32. This is possible by creating an exploit path and then
socially engineering a target user into scanning over the exploit path
using NOD32. If the attacker has write permissions to a directory that is
routinely scanned with NOD32 (such as /tmp), he or she can gain the
privileges of the scanning user (usually root).

Proof of concept exploit code has been written for the FreeBSD 4.7
platform. The following is a sample exploit run that should set up shell
code in an environment variable and spawn a shell under the privileges of
the user executing NOD32:

$ perl eggnod.pl
$ mkdir -p /tmp/`perl -e 'print "A" x 255'`/`perl -e 'print "B" x 240 .
"\xfc\xbf\xbf"'`
$ nod32 /tmp

IV. DETECTION

NOD32 Antivirus System for Unix version 1.012 and below is vulnerable. 

V. VENDOR FIX

The latest version 1.013 fixes the issue and can be downloaded from
http://www.nod32.com

VI. CVE INFORMATION

The Mitre Corp.'s Common Vulnerabilities and Exposures (CVE) Project
assigned the identification number CAN-2003-0062 to this issue.

VII. DISCLOSURE TIMELINE

12/03/2003      Issue disclosed to iDEFENSE
01/28/2003      Eset Software notified (webmaster () nod32 com)
01/28/2003      iDEFENSE clients notified
02/03/2003      Response received from Palo Luka (luka () eset sk)
02/10/2003      Coordinated Public Disclosure

VIII. CREDIT

Knud Erik Højgaard (knud () skodliv dk) discovered this vulnerability.


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