diff --git a/django/forms/fields.py b/django/forms/fields.py
index 14faf2fc36..0aef355d0f 100644
--- a/django/forms/fields.py
+++ b/django/forms/fields.py
@@ -421,7 +421,7 @@ class RegexField(CharField):
 email_re = re.compile(
     r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*"  # dot-atom
     r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*"' # quoted-string
-    r')@(?:[A-Z0-9]+(?:-*[A-Z0-9]+)*\.)+[A-Z]{2,6}$', re.IGNORECASE)  # domain
+    r')@(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?$', re.IGNORECASE)  # domain
 
 class EmailField(RegexField):
     default_error_messages = {
@@ -532,7 +532,7 @@ class ImageField(FileField):
 
 url_re = re.compile(
     r'^https?://' # http:// or https://
-    r'(?:(?:[A-Z0-9]+(?:-*[A-Z0-9]+)*\.)+[A-Z]{2,6}|' #domain...
+    r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?|' #domain...
     r'localhost|' #localhost...
     r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})' # ...or ip
     r'(?::\d+)?' # optional port
diff --git a/tests/regressiontests/forms/fields.py b/tests/regressiontests/forms/fields.py
index 9d9d7227b9..9d407d9ea7 100644
--- a/tests/regressiontests/forms/fields.py
+++ b/tests/regressiontests/forms/fields.py
@@ -767,6 +767,13 @@ u'example@valid-----hyphens.com'
 >>> f.clean('example@valid-with-hyphens.com')
 u'example@valid-with-hyphens.com'
 
+# Check for runaway regex security problem. This will take for-freeking-ever
+# if the security fix isn't in place.
+>>> f.clean('viewx3dtextx26qx3d@yahoo.comx26latlngx3d15854521645943074058')
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Enter a valid e-mail address.']
+
 >>> f = EmailField(required=False)
 >>> f.clean('')
 u''
@@ -972,6 +979,32 @@ ValidationError: [u'Enter a valid URL.']
 Traceback (most recent call last):
 ...
 ValidationError: [u'Enter a valid URL.']
+>>> f.clean('.')
+Traceback (most recent call last):
+...
+ValidationError: [u'Enter a valid URL.']
+>>> f.clean('com.')
+Traceback (most recent call last):
+...
+ValidationError: [u'Enter a valid URL.']
+>>> f.clean('http://example.com.')
+u'http://example.com./'
+>>> f.clean('example.com.')
+u'http://example.com./'
+
+# hangs "forever" if catastrophic backtracking in ticket:#11198 not fixed
+>>> f.clean('http://%s' % ("X"*200,))
+Traceback (most recent call last):
+...
+ValidationError: [u'Enter a valid URL.']
+
+# a second test, to make sure the problem is really addressed, even on 
+# domains that don't fail the domain label length check in the regex
+>>> f.clean('http://%s' % ("X"*60,))
+Traceback (most recent call last):
+...
+ValidationError: [u'Enter a valid URL.']
+
 >>> f.clean('http://.com')
 Traceback (most recent call last):
 ...