Public Vulnerability Reports

Buffer Overflow In NOD32 Antivirus Software for Unix

02.10.03

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 .

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
...

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 .
"xfcxbfxbf"'`
$ nod32 /tmp

DETECTION

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

VENDOR RESPONSE

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

CVE INFORMATION

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

DISCLOSURE TIMELINE

12/03/2002 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

CREDIT

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