diff -r a21a8943c59e -r b3a3bd124ae9 Lib/test/test_bz2.py
--- a/Lib/test/test_bz2.py	Thu Dec 01 11:37:47 2016 -0500
+++ b/Lib/test/test_bz2.py	Thu Dec 01 21:50:01 2016 -0500
@@ -102,6 +102,15 @@
         self.assertRaises(ValueError, BZ2File, os.devnull, compresslevel=0)
         self.assertRaises(ValueError, BZ2File, os.devnull, compresslevel=10)
 
+    def test_uninitialized_object(self):
+        bz2c = BZ2Compressor.__new__(BZ2Compressor)
+        self.assertRaises(ValueError, bz2c.compress, b"foo")
+        self.assertRaises(ValueError, bz2c.flush)
+
+        bz2d = BZ2Decompressor.__new__(BZ2Decompressor)
+        self.assertRaises(ValueError, bz2d.decompress, bytes())
+
+
     def testRead(self):
         self.createTempFile()
         with BZ2File(self.filename) as bz2f:
diff -r a21a8943c59e -r b3a3bd124ae9 Lib/test/test_lzma.py
--- a/Lib/test/test_lzma.py	Thu Dec 01 11:37:47 2016 -0500
+++ b/Lib/test/test_lzma.py	Thu Dec 01 21:50:01 2016 -0500
@@ -58,6 +58,14 @@
         lzd.decompress(empty)
         self.assertRaises(EOFError, lzd.decompress, b"quux")
 
+    def test_uninitialized_object(self):
+        lzc = LZMACompressor.__new__(LZMACompressor)
+        self.assertRaises(LZMAError, lzc.compress, b"foo")
+        self.assertRaises(LZMAError, lzc.flush)
+
+        lzd = LZMADecompressor.__new__(LZMADecompressor)
+        self.assertRaises(LZMAError, lzd.decompress, bytes())
+
     def test_bad_filter_spec(self):
         self.assertRaises(TypeError, LZMACompressor, filters=[b"wobsite"])
         self.assertRaises(ValueError, LZMACompressor, filters=[{"xyzzy": 3}])
diff -r a21a8943c59e -r b3a3bd124ae9 Modules/_bz2module.c
--- a/Modules/_bz2module.c	Thu Dec 01 11:37:47 2016 -0500
+++ b/Modules/_bz2module.c	Thu Dec 01 21:50:01 2016 -0500
@@ -9,6 +9,7 @@
 #include "pythread.h"
 #endif
 
+#include "_compress.h"
 #include <bzlib.h>
 #include <stdio.h>
 
@@ -44,6 +45,7 @@
 #ifdef WITH_THREAD
     PyThread_type_lock lock;
 #endif
+    int initialized;
 } BZ2Compressor;
 
 typedef struct {
@@ -62,6 +64,7 @@
 #ifdef WITH_THREAD
     PyThread_type_lock lock;
 #endif
+    int initialized;
 } BZ2Decompressor;
 
 static PyTypeObject BZ2Compressor_Type;
@@ -237,6 +240,7 @@
 _bz2_BZ2Compressor_compress_impl(BZ2Compressor *self, Py_buffer *data)
 /*[clinic end generated code: output=59365426e941fbcc input=85c963218070fc4c]*/
 {
+    CHECK_INIT(self, "BZ2Compressor", PyExc_ValueError)
     PyObject *result = NULL;
 
     ACQUIRE_LOCK(self);
@@ -262,6 +266,7 @@
 _bz2_BZ2Compressor_flush_impl(BZ2Compressor *self)
 /*[clinic end generated code: output=3ef03fc1b092a701 input=d64405d3c6f76691]*/
 {
+    CHECK_INIT(self, "BZ2Compressor", PyExc_ValueError)
     PyObject *result = NULL;
 
     ACQUIRE_LOCK(self);
@@ -339,6 +344,7 @@
     bzerror = BZ2_bzCompressInit(&self->bzs, compresslevel, 0, 0);
     if (catch_bz2_error(bzerror))
         goto error;
+    self->initialized = 1;
 
     return 0;
 
@@ -618,6 +624,7 @@
                                      Py_ssize_t max_length)
 /*[clinic end generated code: output=23e41045deb240a3 input=52e1ffc66a8ea624]*/
 {
+    CHECK_INIT(self, "BZ2Decompressor", PyExc_ValueError)
     PyObject *result = NULL;
 
     ACQUIRE_LOCK(self);
@@ -670,6 +677,7 @@
     bzerror = BZ2_bzDecompressInit(&self->bzs, 0, 0);
     if (catch_bz2_error(bzerror))
         goto error;
+    self->initialized = 1;
 
     return 0;
 
diff -r a21a8943c59e -r b3a3bd124ae9 Modules/_compress.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Modules/_compress.h	Thu Dec 01 21:50:01 2016 -0500
@@ -0,0 +1,19 @@
+/*
+ * Macros shared between lzma and bz2 modukes
+ */
+
+/*
+ * Check that the compressor/decompressor's __init__ method was called (issue23224).
+ * This avoids a segfault if a compressor/decompressor is created by manually
+ * calling __new__ and then left uninitialized, or if a subclass doesn't call
+ * super() in an overriden __init_- mwthod.
+ *
+ * Since the lzma_allocator struct's alloc function is always set by us during
+ * proper initialization, checking it is sufficient to determine whether
+ * initialization occured.
+ */
+#define CHECK_INIT(self, name, error) if (self->initialized == 0) { \
+        PyErr_Format(error, "%s.__init__() was not called by %s.__init__()", name, Py_TYPE(self)->tp_name); \
+        return NULL; \
+    }
+
diff -r a21a8943c59e -r b3a3bd124ae9 Modules/_lzmamodule.c
--- a/Modules/_lzmamodule.c	Thu Dec 01 11:37:47 2016 -0500
+++ b/Modules/_lzmamodule.c	Thu Dec 01 21:50:01 2016 -0500
@@ -9,6 +9,7 @@
 
 #include "Python.h"
 #include "structmember.h"
+#include "_compress.h"
 #ifdef WITH_THREAD
 #include "pythread.h"
 #endif
@@ -51,6 +52,7 @@
 #ifdef WITH_THREAD
     PyThread_type_lock lock;
 #endif
+    int initialized;
 } Compressor;
 
 typedef struct {
@@ -66,6 +68,7 @@
 #ifdef WITH_THREAD
     PyThread_type_lock lock;
 #endif
+    int initialized;
 } Decompressor;
 
 /* LZMAError class object. */
@@ -564,6 +567,7 @@
 _lzma_LZMACompressor_compress_impl(Compressor *self, Py_buffer *data)
 /*[clinic end generated code: output=31f615136963e00f input=64019eac7f2cc8d0]*/
 {
+    CHECK_INIT(self, "LZMACompressor", Error)
     PyObject *result = NULL;
 
     ACQUIRE_LOCK(self);
@@ -589,6 +593,7 @@
 _lzma_LZMACompressor_flush_impl(Compressor *self)
 /*[clinic end generated code: output=fec21f3e22504f50 input=6b369303f67ad0a8]*/
 {
+    CHECK_INIT(self, "LZMACompressor", Error)
     PyObject *result = NULL;
 
     ACQUIRE_LOCK(self);
@@ -765,6 +770,8 @@
     }
 #endif
 
+    self->initialized = 1;
+
     self->flushed = 0;
     switch (format) {
         case FORMAT_XZ:
@@ -1084,6 +1091,7 @@
                                        Py_ssize_t max_length)
 /*[clinic end generated code: output=ef4e20ec7122241d input=60c1f135820e309d]*/
 {
+    CHECK_INIT(self, "LZMADecompressor", Error)
     PyObject *result = NULL;
 
     ACQUIRE_LOCK(self);
@@ -1196,6 +1204,8 @@
     if (self->unused_data == NULL)
         goto error;
 
+    self->initialized = 1;
+
     switch (format) {
         case FORMAT_AUTO:
             lzret = lzma_auto_decoder(&self->lzs, memlimit_, decoder_flags);