diff -r 1ff29b57628e Lib/test/test_exceptions.py
--- a/Lib/test/test_exceptions.py	Wed Dec 02 14:37:35 2015 +0100
+++ b/Lib/test/test_exceptions.py	Wed Dec 02 14:33:59 2015 -0500
@@ -625,6 +625,32 @@
         obj = wr()
         self.assertTrue(obj is None, "%s" % obj)
 
+    def testExceptionChainedContext(self):
+        class Err1(Exception): pass
+        class Err2(Exception): pass
+
+        err1 = Err1()
+        with self.assertRaisesRegex(TypeError, 'cycle in exception context'):
+            err1.__context__ = err1
+
+        err2 = Err2()
+        err2.__context__ = err1
+        with self.assertRaisesRegex(TypeError, 'cycle in exception context'):
+            err1.__context__ = err2
+
+    def testExceptionChainedCause(self):
+        class Err1(Exception): pass
+        class Err2(Exception): pass
+
+        err1 = Err1()
+        with self.assertRaisesRegex(TypeError, 'cycle in exception cause'):
+            err1.__cause__ = err1
+
+        err2 = Err2()
+        err2.__cause__ = err1
+        with self.assertRaisesRegex(TypeError, 'cycle in exception cause'):
+            err1.__cause__ = err2
+
     def test_exception_target_in_nested_scope(self):
         # issue 4617: This used to raise a SyntaxError
         # "can not delete variable 'e' referenced in nested scope"
diff -r 1ff29b57628e Objects/exceptions.c
--- a/Objects/exceptions.c	Wed Dec 02 14:37:35 2015 +0100
+++ b/Objects/exceptions.c	Wed Dec 02 14:33:59 2015 -0500
@@ -265,6 +265,10 @@
         Py_INCREF(arg);
     }
     PyException_SetContext(self, arg);
+    if (arg != NULL && ((PyBaseExceptionObject *)self)->context == NULL) {
+        PyErr_SetString(PyExc_TypeError, "cycle in exception context chain");
+        return -1;
+    }
     return 0;
 }
 
@@ -292,6 +296,10 @@
         Py_INCREF(arg);
     }
     PyException_SetCause(self, arg);
+    if (arg != NULL && ((PyBaseExceptionObject *)self)->cause == NULL) {
+        PyErr_SetString(PyExc_TypeError, "cycle in exception cause chain");
+        return -1;
+    }
     return 0;
 }
 
@@ -331,6 +339,14 @@
 /* Steals a reference to cause */
 void
 PyException_SetCause(PyObject *self, PyObject *cause) {
+    PyObject *exc = cause;
+    while (exc != NULL) {
+        if (exc == self) {
+            cause = NULL;
+            break;
+        }
+        exc = ((PyBaseExceptionObject *)exc)->cause;
+    }
     PyObject *old_cause = ((PyBaseExceptionObject *)self)->cause;
     ((PyBaseExceptionObject *)self)->cause = cause;
     ((PyBaseExceptionObject *)self)->suppress_context = 1;
@@ -346,7 +362,16 @@
 
 /* Steals a reference to context */
 void
-PyException_SetContext(PyObject *self, PyObject *context) {
+PyException_SetContext(PyObject *self, PyObject *context)
+{
+    PyObject *exc = context;
+    while (exc != NULL) {
+        if (exc == self) {
+            context = NULL;
+            break;
+        }
+        exc = ((PyBaseExceptionObject *)exc)->context;
+    }
     PyObject *old_context = ((PyBaseExceptionObject *)self)->context;
     ((PyBaseExceptionObject *)self)->context = context;
     Py_XDECREF(old_context);