Add release note for GL !11565

diff --git a/doc/notes/notes-9.20.20.rst b/doc/notes/notes-9.20.20.rst
index 9803fb8d0bccdb0845b8866b2f98baa188cdd3b3..cf87f30e5306b919736f8cc1fc62243a6cd1d852 100644 (file)
--- a/doc/notes/notes-9.20.20.rst
+++ b/doc/notes/notes-9.20.20.rst
@@ -88,3 +88,11 @@ Bug Fixes
   the import function might overflow. This could lead to a memory
   corruption on the stack and ultimately a server crash. This has been
   fixed. :gl:`#5758`
+
+- Return FORMERR for queries with the EDNS Client Subnet FAMILY field
+  set to 0.
+
+  :rfc:`7871` only defines families 1 (IPv4) and 2 (IPv6), and requires
+  FORMERR to be returned for all unknown families. Queries with the EDNS
+  Client Subnet FAMILY field set to 0 now elicit responses with
+  RCODE=FORMERR. :gl:`!11565`