diff --git a/lib/rack/utils.rb b/lib/rack/utils.rb
index d2c8bc440..fc6e8a2b1 100644
--- a/lib/rack/utils.rb
+++ b/lib/rack/utils.rb
@@ -28,6 +28,14 @@ def unescape(s)
 
     DEFAULT_SEP = /[&;] */n
 
+    class << self
+      attr_accessor :key_space_limit
+    end
+
+    # The default number of bytes to allow parameter keys to take up.
+    # This helps prevent a rogue client from flooding a Request.
+    self.key_space_limit = 65536
+
     # Stolen from Mongrel, with some small modifications:
     # Parses a query string by breaking it up at the '&'
     # and ';' characters.  You can also use this to parse
@@ -36,8 +44,19 @@ def unescape(s)
     def parse_query(qs, d = nil)
       params = {}
 
+      max_key_space = Utils.key_space_limit
+      bytes = 0
+
       (qs || '').split(d ? /[#{d}] */n : DEFAULT_SEP).each do |p|
         k, v = p.split('=', 2).map { |x| unescape(x) }
+
+        if k
+          bytes += k.size
+          if bytes > max_key_space
+            raise RangeError, "exceeded available parameter key space"
+          end
+        end
+
         if cur = params[k]
           if cur.class == Array
             params[k] << v
@@ -56,8 +75,19 @@ def parse_query(qs, d = nil)
     def parse_nested_query(qs, d = nil)
       params = {}
 
+      max_key_space = Utils.key_space_limit
+      bytes = 0
+
       (qs || '').split(d ? /[#{d}] */n : DEFAULT_SEP).each do |p|
         k, v = unescape(p).split('=', 2)
+
+        if k
+          bytes += k.size
+          if bytes > max_key_space
+            raise RangeError, "exceeded available parameter key space"
+          end
+        end
+
         normalize_params(params, k, v)
       end
 
@@ -489,6 +519,9 @@ def self.parse_multipart(env)
 
           rx = /(?:#{EOL})?#{Regexp.quote boundary}(#{EOL}|--)/n
 
+          max_key_space = Utils.key_space_limit
+          bytes = 0
+
           loop {
             head = nil
             body = ''
@@ -503,6 +536,13 @@ def self.parse_multipart(env)
                 content_type = head[/Content-Type: (.*)#{EOL}/ni, 1]
                 name = head[/Content-Disposition:.*\s+name="?([^\";]*)"?/ni, 1] || head[/Content-ID:\s*([^#{EOL}]*)/ni, 1]
 
+                if name
+                  bytes += name.size
+                  if bytes > max_key_space
+                    raise RangeError, "exceeded available parameter key space"
+                  end
+                end
+
                 if content_type || filename
                   body = Tempfile.new("RackMultipart")
                   body.binmode  if body.respond_to?(:binmode)
diff --git a/test/spec_rack_request.rb b/test/spec_rack_request.rb
index fcdeb4844..a34a9675f 100644
--- a/test/spec_rack_request.rb
+++ b/test/spec_rack_request.rb
@@ -79,6 +79,32 @@
     req.params.should.equal "foo" => "bar", "quux" => "bla"
   end
 
+  specify "limit the keys from the GET query string" do
+    env = Rack::MockRequest.env_for("/?foo=bar")
+
+    old, Rack::Utils.key_space_limit = Rack::Utils.key_space_limit, 1
+    begin
+      req = Rack::Request.new(env)
+      lambda { req.GET }.should.raise(RangeError)
+    ensure
+      Rack::Utils.key_space_limit = old
+    end
+  end
+
+  specify "limit the keys from the POST form data" do
+    env = Rack::MockRequest.env_for("",
+            "REQUEST_METHOD" => 'POST',
+            :input => "foo=bar&quux=bla")
+
+    old, Rack::Utils.key_space_limit = Rack::Utils.key_space_limit, 1
+    begin
+      req = Rack::Request.new(env)
+      lambda { req.POST }.should.raise(RangeError)
+    ensure
+      Rack::Utils.key_space_limit = old
+    end
+  end
+
   specify "can parse POST data with explicit content type regardless of method" do
     req = Rack::Request.new \
       Rack::MockRequest.env_for("/",
@@ -295,6 +321,29 @@
       req.media_type_params['bling'].should.equal 'bam'
   end
 
+  specify "raise RangeError if the key space is exhausted" do
+    input = <<EOF
+--AaB03x\r
+Content-Disposition: form-data; name="text"\r
+Content-Type: text/plain; charset=US-ASCII\r
+\r
+contents\r
+--AaB03x--\r
+EOF
+
+    env = Rack::MockRequest.env_for("/", 
+                      "CONTENT_TYPE" => "multipart/form-data, boundary=AaB03x",
+                      "CONTENT_LENGTH" => input.size,
+                      :input => input)
+
+    old, Rack::Utils.key_space_limit = Rack::Utils.key_space_limit, 1
+    begin
+      lambda { Rack::Utils::Multipart.parse_multipart(env) }.should.raise(RangeError)
+    ensure
+      Rack::Utils.key_space_limit = old
+    end
+  end
+
   specify "can parse multipart form data" do
     # Adapted from RFC 1867.
     input = <<EOF