diff --git a/doc/arm/notes.rst b/doc/arm/notes.rst
index ba33babf79..333624d83e 100644
--- a/doc/arm/notes.rst
+++ b/doc/arm/notes.rst
@@ -45,6 +45,7 @@ The list of known issues affecting the latest version in the 9.20 branch can be
 found at
 https://gitlab.isc.org/isc-projects/bind9/-/wikis/Known-Issues-in-BIND-9.20
 
+.. include:: ../notes/notes-9.20.21.rst
 .. include:: ../notes/notes-9.20.20.rst
 .. include:: ../notes/notes-9.20.19.rst
 .. include:: ../notes/notes-9.20.18.rst
diff --git a/doc/notes/notes-9.20.21.rst b/doc/notes/notes-9.20.21.rst
new file mode 100644
index 0000000000..1ba9a82197
--- /dev/null
+++ b/doc/notes/notes-9.20.21.rst
@@ -0,0 +1,77 @@
+.. Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+..
+.. SPDX-License-Identifier: MPL-2.0
+..
+.. This Source Code Form is subject to the terms of the Mozilla Public
+.. License, v. 2.0.  If a copy of the MPL was not distributed with this
+.. file, you can obtain one at https://mozilla.org/MPL/2.0/.
+..
+.. See the COPYRIGHT file distributed with this work for additional
+.. information regarding copyright ownership.
+
+Notes for BIND 9.20.21
+----------------------
+
+Security Fixes
+~~~~~~~~~~~~~~
+
+- [CVE-2026-1519] Fix unbounded NSEC3 iterations when validating
+  referrals to unsigned delegations.
+
+  DNSSEC-signed zones may contain high iteration-count NSEC3 records,
+  which prove that certain delegations are insecure. Previously, a
+  validating resolver encountering such a delegation processed these
+  iterations up to the number given, which could be a maximum of 65,535.
+  This has been addressed by introducing a processing limit, set at 50.
+  Now, if such an NSEC3 record is encountered, the delegation will be
+  treated as insecure.
+
+  ISC would like to thank Samy Medjahed/Ap4sh for bringing this
+  vulnerability to our attention. :gl:`#5708`
+
+- [CVE-2026-3104] Fix memory leaks in code preparing DNSSEC proofs of
+  non-existence.
+
+  An attacker controlling a DNSSEC-signed zone could trigger a memory
+  leak in the logic preparing DNSSEC proofs of non-existence, by
+  creating more than :any:`max-records-per-type` RRSIGs for NSEC
+  records. These memory leaks have been fixed.
+
+  ISC would like to thank Vitaly Simonovich for bringing this
+  vulnerability to our attention. :gl:`#5742`
+
+- [CVE-2026-3119] Prevent a crash in code processing queries containing
+  a TKEY record.
+
+  The :iscman:`named` process could terminate unexpectedly when
+  processing a correctly signed query containing a TKEY record. This has
+  been fixed.
+
+  ISC would like to thank Vitaly Simonovich for bringing this
+  vulnerability to our attention. :gl:`#5748`
+
+- [CVE-2026-3591] Fix a stack use-after-return flaw in SIG(0) handling
+  code.
+
+  A stack use-after-return flaw in SIG(0) handling code could enable ACL
+  bypass and/or assertion failures in certain circumstances. This flaw
+  has been fixed.
+
+  ISC would like to thank Mcsky23 for bringing this vulnerability to our
+  attention. :gl:`#5754`
+
+Bug Fixes
+~~~~~~~~~
+
+- Resolve "key defined in view is not found"
+
+  Commit `2956e4fc` hardened the `key` name check when used in
+  `primaries` to reject the configuration if the key was not defined,
+  rather than simply checking whether the key name was correctly formed.
+
+  However, the key name check didn't include the view configuration,
+  causing keys not to be recognized if they were defined inside the view
+  and not at the global level.  This regression is now fixed.
+  :gl:`#5761`
+
+