Issue #18747: document issue with OpenSSL's CPRNG state and fork
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 59457f7..2c33366 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -2582,6 +2582,10 @@
    Note that some platforms including FreeBSD <= 6.3, Cygwin and OS/2 EMX have
    known issues when using fork() from a thread.
 
+   .. warning::
+
+      See :mod:`ssl` for applications that use the SSL module with fork().
+
    Availability: Unix.