Issue #13885: CVE-2011-3389: the _ssl module would always disable the CBC IV attack countermeasure.

Misc/NEWS

@@ -13,6 +13,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #13885: CVE-2011-3389: the _ssl module would always disable the CBC
+  IV attack countermeasure.
+
 - Issue #11603: Fix a crash when __str__ is rebound as __repr__.  Patch by
   Andreas Stührk.
 

Modules/_ssl.c

@@ -365,7 +365,8 @@ newPySSLObject(PySocketSockObject *Sock, char *key_file, char *cert_file,
     }
 
     /* ssl compatibility */
-    SSL_CTX_set_options(self->ctx, SSL_OP_ALL);
+    SSL_CTX_set_options(self->ctx,
+                        SSL_OP_ALL & ~SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS);
 
     verification_mode = SSL_VERIFY_NONE;
     if (certreq == PY_SSL_CERT_OPTIONAL)