1 files changed, 5 insertions, 0 deletions
diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index 9714ddff16..b170b3885e 100644
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -1203,6 +1203,11 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
                      1);
      */
     if (fileno != -1 && fileno != 0) {
+        /* Ensure that fileno is within the CRT's valid range */
+        if (_PyVerify_fd(fileno) == 0) {
+            PyErr_SetFromErrno(mmap_module_error);
+            return NULL;
+        }
         fh = (HANDLE)_get_osfhandle(fileno);
         if (fh==(HANDLE)-1) {
             PyErr_SetFromErrno(mmap_module_error);