diff -r cc0fc4e9b494 Python/dtoa.c
--- a/Python/dtoa.c	Sat Nov 23 21:14:42 2013 +0200
+++ b/Python/dtoa.c	Sat Nov 23 19:45:38 2013 +0000
@@ -207,6 +207,12 @@
 #define MAX_ABS_EXP 19999U
 #endif
 
+/* maximum permitted number of significant digits in the strtod input.
+   This should be chosen to safely fit into an int. */
+#ifndef MAX_SIGNIFICANT_DIGITS
+#define MAX_SIGNIFICANT_DIGITS 2000000000
+#endif
+
 /* The following definition of Storeinc is appropriate for MIPS processors.
  * An alternative that might be better on some machines is
  * #define Storeinc(a,b,c) (*a++ = b << 16 | c & 0xffff)
@@ -1585,6 +1591,14 @@
         nd += s - s1;
     }
 
+    /* If there are more than MAX_SIGNIFICANT_DIGITS digits, report
+       a parse error. */
+    if (nd > MAX_SIGNIFICANT_DIGITS) {
+        if (se)
+            *se = (char *)s00;
+        goto parse_error;
+    }
+
     /* Now lz is true if and only if there were leading zero digits, and nd
        gives the total number of digits ignoring leading zeros.  A valid input
        must have at least one digit. */