diff --git a/addons/mail/controllers/discuss.py b/addons/mail/controllers/discuss.py
index 94d10a0fa03..d0edbfff24d 100644
--- a/addons/mail/controllers/discuss.py
+++ b/addons/mail/controllers/discuss.py
@@ -257,17 +257,20 @@ class DiscussController(http.Controller):
         if channel_partner.env.user.share:
             # Only generate the access token if absolutely necessary (= not for internal user).
             vals['access_token'] = channel_partner.env['ir.attachment']._generate_access_token()
-        attachment = channel_partner.env['ir.attachment'].create(vals)
-        attachment._post_add_create()
-        attachmentData = {
-            'filename': ufile.filename,
-            'id': attachment.id,
-            'mimetype': attachment.mimetype,
-            'name': attachment.name,
-            'size': attachment.file_size
-        }
-        if attachment.access_token:
-            attachmentData['accessToken'] = attachment.access_token
+        try:
+            attachment = channel_partner.env['ir.attachment'].create(vals)
+            attachment._post_add_create()
+            attachmentData = {
+                'filename': ufile.filename,
+                'id': attachment.id,
+                'mimetype': attachment.mimetype,
+                'name': attachment.name,
+                'size': attachment.file_size
+            }
+            if attachment.access_token:
+                attachmentData['accessToken'] = attachment.access_token
+        except AccessError:
+            attachmentData = {'error': _("You are not allowed to upload an attachment here.")}
         return request.make_response(
             data=json.dumps(attachmentData),
             headers=[('Content-Type', 'application/json')]
diff --git a/addons/mail/i18n/mail.pot b/addons/mail/i18n/mail.pot
index 6559226b383..23cabce156e 100644
--- a/addons/mail/i18n/mail.pot
+++ b/addons/mail/i18n/mail.pot
@@ -1374,6 +1374,14 @@ msgstr ""
 msgid "Channel"
 msgstr ""
 
+#. module: mail
+#: code:addons/mail/models/mail_channel.py:0
+#, python-format
+msgid ""
+"Channel \"%(channel_name)s\" only accepts members of group "
+"\"%(group_name)s\". Forbidden for: %(guest_names)s"
+msgstr ""
+
 #. module: mail
 #: code:addons/mail/models/mail_channel.py:0
 #, python-format
@@ -7512,6 +7520,12 @@ msgstr ""
 msgid "You are in channel <b>#%s</b>."
 msgstr ""
 
+#. module: mail
+#: code:addons/mail/controllers/discuss.py:0
+#, python-format
+msgid "You are not allowed to upload an attachment here."
+msgstr ""
+
 #. module: mail
 #. openerp-web
 #: code:addons/mail/static/src/models/discuss_sidebar_category_item/discuss_sidebar_category_item.js:0
diff --git a/addons/web/controllers/binary.py b/addons/web/controllers/binary.py
index 7883635dea6..77afdd27c82 100644
--- a/addons/web/controllers/binary.py
+++ b/addons/web/controllers/binary.py
@@ -11,8 +11,9 @@ import unicodedata
 import odoo
 import odoo.modules.registry
 from odoo import http
-from odoo.modules import get_resource_path
+from odoo.exceptions import AccessError
 from odoo.http import request
+from odoo.modules import get_resource_path
 from odoo.tools import pycompat
 from odoo.tools.mimetypes import guess_mimetype
 from odoo.tools.misc import file_open, file_path
@@ -131,6 +132,8 @@ class Binary(http.Controller):
                     'res_id': int(id)
                 })
                 attachment._post_add_create()
+            except AccessError:
+                args.append({'error': _("You are not allowed to upload an attachment here.")})
             except Exception:
                 args.append({'error': _("Something horrible happened")})
                 _logger.exception("Fail to upload attachment %s", ufile.filename)
diff --git a/addons/web/i18n/web.pot b/addons/web/i18n/web.pot
index e8ed4906240..99d93c5e6e2 100644
--- a/addons/web/i18n/web.pot
+++ b/addons/web/i18n/web.pot
@@ -4824,6 +4824,12 @@ msgstr ""
 msgid "Yesterday"
 msgstr ""
 
+#. module: web
+#: code:addons/web/controllers/main.py:0
+#, python-format
+msgid "You are not allowed to upload an attachment here."
+msgstr ""
+
 #. module: web
 #. openerp-web
 #: code:addons/web/static/src/legacy/js/widgets/model_field_selector.js:0