diff -r 5c091acc799f Modules/_ssl.c
--- a/Modules/_ssl.c	Sat Aug 17 17:25:27 2013 +0200
+++ b/Modules/_ssl.c	Sat Aug 17 17:58:47 2013 +0200
@@ -51,6 +51,11 @@
 #include <sys/poll.h>
 #endif
 
+#ifdef HAVE_PTHREAD_ATFORK
+#include <pthread.h>
+#include <time.h>
+#endif
+
 /* Include OpenSSL header files */
 #include "openssl/rsa.h"
 #include "openssl/crypto.h"
@@ -2936,8 +2941,84 @@
 Returns number of bytes read.  Raises SSLError if connection to EGD\n\
 fails or if it does not provide enough data to seed PRNG.");
 
+/* Seed OpenSSL's PRNG at fork(), http://bugs.python.org/issue18747
+ *
+ * The child handler seeds the PRNG from pseudo-random data like pid, the
+ * current time (nanoseconds, miliseconds or seconds) and an uninitialized
+ * array. The array contains stack variables that are impossible to predict
+ * on most systems, e.g. function return address (subject to ASLR), the
+ * stack protection canary and automatic variables.
+ * The code is inspired by Apache's ssl_rand_seed() function.
+ *
+ * Note:
+ * The code uses pthread_atfork() until Python has a proper atfork API. The
+ * handlers are not removed from the child process.
+ */
+
+#ifdef HAVE_PTHREAD_ATFORK
+static void
+PySSL_RAND_atfork_child(void)
+{
+    /* OpenSSL's PRNG processes seeds in blocks of 20 bytes. */
+    struct {
+        char stack[64]; /* uninitialized (!) stack data, 64 because OpenSSL
+                         * processes seed in blocks of 20 bytes. */
+        pid_t pid;      /* current pid */
+        long time;      /* current nano, micro or full seconds */
+    } seed;
+#ifdef HAVE_CLOCK_GETTIME
+    struct timespec ts;
+#elif defined(HAVE_GETTIMEOFDAY)
+    struct timeval tv;
 #endif
 
+#ifdef WITH_VALGRIND
+    VALGRIND_MAKE_MEM_DEFINED(seed.stack, sizeof(seed.stack));
+#endif
+
+    seed.pid = getpid();
+    seed.time = 0;
+#ifdef HAVE_CLOCK_GETTIME
+    if (clock_gettime(CLOCK_REALTIME, &ts) == 0)
+        seed.time = ts.tv_nsec;
+#elif defined(HAVE_GETTIMEOFDAY)
+    if (gettimeofday(&tv, NULL) == 0) {
+        seed.time = tv.tv_usec;
+#endif
+    if (seed.time == 0)
+        seed.time = time(NULL);
+
+#if 1
+    fprintf(stderr, "PySSL_RAND_atfork_child() seeds %i bytes in %i\n",
+            (int)sizeof(seed), seed.pid);
+#endif
+    RAND_add((unsigned char *)&seed, sizeof(seed), 0.0);
+}
+
+static int
+PySSL_RAND_atfork(void)
+{
+    static int registered = 0;
+    int retval;
+
+    if (registered)
+        return 0;
+
+    retval = pthread_atfork(NULL,                     /* prepare */
+                            NULL,                     /* parent */
+                            PySSL_RAND_atfork_child); /* child */
+    if (retval != 0) {
+        PyErr_SetFromErrno(PyExc_OSError);
+        return -1;
+    }
+    registered = 1;
+    return 0;
+}
+#endif /* HAVE_PTHREAD_ATFORK */
+
+#endif /* HAVE_OPENSSL_RAND */
+
+
 PyDoc_STRVAR(PySSL_get_default_verify_paths_doc,
 "get_default_verify_paths() -> tuple\n\
 \n\
@@ -3533,5 +3614,10 @@
     if (r == NULL || PyModule_AddObject(m, "_OPENSSL_API_VERSION", r))
         return NULL;
 
+#if defined(HAVE_OPENSSL_RAND) && defined(HAVE_PTHREAD_ATFORK)
+    if (PySSL_RAND_atfork() == -1)
+        return NULL;
+#endif
+
     return m;
 }
diff -r 5c091acc799f configure
--- a/configure	Sat Aug 17 17:25:27 2013 +0200
+++ b/configure	Sat Aug 17 17:58:47 2013 +0200
@@ -9809,6 +9809,17 @@
 fi
 done
 
+      for ac_func in pthread_atfork
+do :
+  ac_fn_c_check_func "$LINENO" "pthread_atfork" "ac_cv_func_pthread_atfork"
+if test "x$ac_cv_func_pthread_atfork" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_PTHREAD_ATFORK 1
+_ACEOF
+
+fi
+done
+
 fi
 
 
diff -r 5c091acc799f configure.ac
--- a/configure.ac	Sat Aug 17 17:25:27 2013 +0200
+++ b/configure.ac	Sat Aug 17 17:58:47 2013 +0200
@@ -2512,6 +2512,7 @@
             [Define if pthread_sigmask() does not work on your system.])
             ;;
         esac])
+      AC_CHECK_FUNCS(pthread_atfork)
 fi
 
 
diff -r 5c091acc799f pyconfig.h.in
--- a/pyconfig.h.in	Sat Aug 17 17:25:27 2013 +0200
+++ b/pyconfig.h.in	Sat Aug 17 17:58:47 2013 +0200
@@ -633,6 +633,9 @@
 /* Define if your compiler supports function prototype */
 #undef HAVE_PROTOTYPES
 
+/* Define to 1 if you have the `pthread_atfork' function. */
+#undef HAVE_PTHREAD_ATFORK
+
 /* Defined for Solaris 2.6 bug in pthread header. */
 #undef HAVE_PTHREAD_DESTRUCTOR