diff --git a/octavia/common/exceptions.py b/octavia/common/exceptions.py
index 6f0994d394..53cf020a36 100644
--- a/octavia/common/exceptions.py
+++ b/octavia/common/exceptions.py
@@ -133,6 +133,12 @@ class UnreadablePKCS12(APIException):
     code = 400
 
 
+class MissingCertSubject(APIException):
+    msg = _('No CN or DNSName(s) found in certificate. The certificate is '
+            'invalid.')
+    code = 400
+
+
 class MisMatchedKey(OctaviaException):
     message = _("Key and x509 certificate do not match")
 
diff --git a/octavia/common/tls_utils/cert_parser.py b/octavia/common/tls_utils/cert_parser.py
index 474b410ca5..f1e6e8dbe6 100644
--- a/octavia/common/tls_utils/cert_parser.py
+++ b/octavia/common/tls_utils/cert_parser.py
@@ -256,14 +256,16 @@ def get_host_names(certificate):
     """
     if isinstance(certificate, str):
         certificate = certificate.encode('utf-8')
+    host_names = {'cn': None, 'dns_names': []}
     try:
         cert = x509.load_pem_x509_certificate(certificate,
                                               backends.default_backend())
-        cn = cert.subject.get_attributes_for_oid(x509.OID_COMMON_NAME)[0]
-        host_names = {
-            'cn': cn.value.lower(),
-            'dns_names': []
-        }
+        try:
+            cn = cert.subject.get_attributes_for_oid(x509.OID_COMMON_NAME)[0]
+            host_names['cn'] = cn.value.lower()
+        except Exception as e:
+            LOG.debug(f'Unable to get CN from certificate due to: {e}. '
+                      f'Assuming subject alternative names are present.')
         try:
             ext = cert.extensions.get_extension_for_oid(
                 x509.OID_SUBJECT_ALTERNATIVE_NAME
@@ -274,7 +276,17 @@ def get_host_names(certificate):
             LOG.debug("%s extension not found",
                       x509.OID_SUBJECT_ALTERNATIVE_NAME)
 
+        # Certs with no subject are valid as long as a subject alternative
+        # name is present. If both are missing, it is an invalid cert per
+        # the x.509 standard.
+        if not host_names['cn'] and not host_names['dns_names']:
+            LOG.warning('No CN or DNSName(s) found in certificate. The '
+                        'certificate is invalid.')
+            raise exceptions.MissingCertSubject()
+
         return host_names
+    except exceptions.MissingCertSubject:
+        raise
     except Exception as e:
         LOG.exception('Unreadable Certificate.')
         raise exceptions.UnreadableCert from e
@@ -359,6 +371,10 @@ def load_certificates_data(cert_mngr, obj, context=None):
                 cert_mngr.get_cert(context,
                                    obj.tls_certificate_id,
                                    check_only=True))
+        except exceptions.MissingCertSubject:
+            # This was logged below, so raise as is to provide a clear
+            # user error
+            raise
         except Exception as e:
             LOG.warning('Unable to retrieve certificate: %s due to %s.',
                         obj.tls_certificate_id, str(e))
diff --git a/octavia/tests/common/sample_certs.py b/octavia/tests/common/sample_certs.py
index b798793490..a22198effb 100644
--- a/octavia/tests/common/sample_certs.py
+++ b/octavia/tests/common/sample_certs.py
@@ -872,3 +872,118 @@ phYuPfZekoNbsOIPDTiPFniuP2saOF4TSRCW4KnpgblRkds6c8X+1ExdlSo5GjNa
 PftOKlYtE7T7Kw4CI9+O2H38IUOYjDt/c2twy954K4pKe4x9Ud8mImpS/oEzOsoz
 /Mn++bjO55LdaAUKQ3wa8LZ5WFB+Gs6b2kmBfzGarWEiX64=
 -----END X509 CRL-----"""
+
+# An invalid certificate due to no subject and no subjectAltName
+NOCN_NOSUBALT_CRT = b"""-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----"""
+
+# A certificate with no subject but with Subject Alternative Name
+NOCN_SUBALT_CRT = b"""-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----"""
+
+NOCN_SUBALT_KEY = b"""-----BEGIN PRIVATE KEY-----
+MIIJQgIBADANBgkqhkiG9w0BAQEFAASCCSwwggkoAgEAAoICAQCgPPtIic8edZE7
+n5iKcRgjPylBVnSdFDJjjzdTZskjWo+pxiPyMeptdwOUmns4W0ZSbxMDex6oPrZf
+n6rtEYLUDl3wQzIiZvpAJdAkIjh+11ONT+n8pP0C/Fhd1VRgbWsE1p98fScOyLXf
+8xa/mnqUDo+SyMHMdZ3B163lnTC6g2uz6VtUbugVtBSlcV+lmEK9jyNPJxCMbug8
+y3Gix5LUcjWIO6/V/WtLS2XKeTAgRt4dxLVYFJC/asPKumnCaQxgRe7LEUzQ390F
+EoNI6385A/ViQout9bXn3QJAzSGVxmYIG1rAxj7Hl+CRvae1hsz8eUGNg5DKgyao
+uhaEt+bU/ljXGNJ/VaAUF7VxVfwKjgtO9DcK4cbDQN3AW6UahEGCbCA2l6tHJhUe
+GqA1pODl6rOyPnacojBXkRxFO4eA6cM2jpjsmkps7GahDBtpbHSWZgvnyBZMirT9
+AUL/5qL1mNuaCUqReeEPz3cCp+jxTtm0VUi0rZa4abql8Nvgs5UE+mAgM/mo6g55
+/8PDSK0+svg4hXfpLVgnnf6OGQc7MTnsUaYfrdG3ZE5kfDzaZx8HMc1Td94AknOk
+OQ1tfzNlfFRmKpz3f7WhGjJR5v8EN8tv2h/7ZMqvOTzObagm1LHA+E1Ge0epG9JP
+NwJNomTjOUR2+M3OKZq3jSiz34K0OwIDAQABAoICABC+7r/g7w1O2hOyFR36vbwJ
+QMV8RImZ774p3G1R45lXQIZMl7sa7lXsRyqDjncQSuQYiZMmjcilbSfHJvTJjLOe
+oMCYNSgVPPfxO7RbAy52UFwHSvvFPk/OkWmU/tFo/fMuftJive80mJVD8U+q1D6e
+2vBLHL3CWO9GG/1QFSSY0Wum6o2DXavO+w1jMMy8gdUPnXALNBaJDKo11LVfR//9
+w4xuOG0To9/ljEjBq37kCRhxU0ZWN95ZSQbpvl273rg89rywHSgDDTUXfzLisZQC
+zuUq8TAH6q/FkBO3nFfruQQF39EfprXzMFvqxxkYclm8TlZ8tmgDlsmxUOMj2PKl
+H9kWDC5YkynfkxltKgiEJ9Kc3pZnfaScABnz0GySsZN71bUbr7fBqwH0LhbZiQqa
+b9pWcbyKuGFJ56gVsokVHcpKnKmKHedtmL33oJzI3iWYZls/mPejmkwIWt1i3F7c
+ZnhDJJp3gWgzZzSyV5OjZ05SIrM9er9r+WqS75ns7vKEzhgzpHdZuUR2jNNVu/EA
+rCnsebUtemr0tDYxhI5BcPgj3fzq02u7plJUFIwlPrpMxZ8VBJgoSwT7Di5qpHnt
+LmiGoqRM+vVXiWshops1I7q7zLCgvP+Difi4KNjap/lBsj7hiB7alZTrMVVAXiBr
+Ia++3L38ga5DJ+SHDzjBAoIBAQDNUG4URQD/j0E3pS4zn4wezSp0wOTKKIw2Z6oU
+02reZq9uFLIt+/74DVy3NZm3tBgeSakYUZeDB8zpog3mGpkPAHpwObB/fPbMYmst
+cCnXYDf9Uvb7k287a0GIbCOXwkHSrgRwznAZ4EQp6E0nZSoLbyZiC+uhYEVZgQQo
+JswsjKCSaL7o/4XXQOi6Mdsd4BX7aVVKjYrQZ8TkkCsMYFdQMSL1fB8DW4Q+Ixco
+6BGXPoaav/2XOb0HGBmrXX/yqllA8rw0U7RNLgsE7gZIlltGeTsQMeo/+w5+LJKt
+HOhhEUHITJkRZ7P/S8OdXXoVCNiUzCxGy/LrHW/AWu0t1WWbAoIBAQDHy9Allaod
+WDxdbe5G5ke03WFcPoVAxOWu0mloaFdbd7Ec39y4vr1hxRZz+SEUdouCie1nVB3P
+sj2lPJ44qKS8triqNCuEalpMHaTBdIyjItqh1l66fLA1/FYxAM7cxcz5rBVK2zvf
+KrT3LNmzVpbltl3nPQhvAKEV8zEdSVze6Z0K6QbZP8WfPtCiQYMAjeNu48AIp/+t
+pxJbkcmWLIYixfiJbHfe0LUu/P3rk0WDCHnheVzOTSE8XzGqnIxyv6w4rYOl9IeT
+SnYublICJHOTp6gKuiIieGD7TC14DB8vYbSc0+opIvYYItcS//laLOD+eLUgZx5K
+Wb4ubbosnyXhAoIBAFGzQsqgFuCbQemBupviTmDnZZCmPaTQc9Mmd0DoTGuJ0x9r
+7udrkq9kqdNh6fR3Hu3WhApgVXlXvkvuJ7e8N9IHb7F+02Q39wGn3FxteMjyyfTt
+ccj0h1vOt3oxBgzayVSr2KqHC4bQfm9quGEH2a5JIa38blx+MbqHI39SyQalQzRf
+qDCRldHtS27kbfw6cqTj6oPLRUTfNjN5xxeassP/eZjUNocggMQ1NH8bsfxMbkXg
+RmpKGJVdGsHdaA/Jh9DXhtsPv/zCaLIiga+a3WFy1nUAV+Xz4nWFCS0IBtSxiErL
+aFHLwY3CuWnCi9UY+w5jHO9jMxwqT5Ds3drSQycCggEBALoewFEy4d0iRGGYtb6w
+aJ4xGLBwwXt7sKcx9eXARZi8oG5QkHI9pXg9vFPfAZTpdb7uNAzszDSeS1TxakdH
+uubdpJtRrDRXSrTbbI6Wvyh9oIPgijBZVWGFJtnRceMyFGeFifRI1LZpN1mHG2o4
+QKvPPhzau0+Em4syGE+69tvlblkqiSm6gaN+RabRNnM+ul6jpVGrBsBDAhPxdIQE
+CBS+rW9/bw9PB2m1XemlML0HGVsUzoKUUWDHISJZYXDH42yNHzVq3R014XARby31
+vQEQzrbnfEL2NwoChdzuFeLytujddKZLnksPsaFOeYAqjJIh6kE8Lnh+r27a4vMM
+cqECggEAAx1DVI43AMBfSbAs5C41vjRdjMrZtxfKIpFjj1whGj/JzLKdMdqqH+Ai
++R6NI7IB88pGHlCOmdEpfbr4Cq1ZnizA3yLV9sluMz1bpHlIDsCIp+1VkQYKfsEv
+upZy82MtfGtG3BSLn+GCTzLJcTN6KINg98Xivp/WsRAEvwT/w1o4iJMgzKmTET2I
+UGJfZcF0WeSVo34FNArfXyfXPvPV7mi08Z6fQuUnFvH9tGZs5Y9mUUSgXXEDSjKY
+ZHliqmDNGub7rMy6/0wDOWiS4pi/w8FeCyBvbx23rj6i+FLO6GK+5B7TaCxjOVbk
+SYVTfCHpvJIgjRkRMP2yZCk3g6T4XA==
+-----END PRIVATE KEY-----"""
diff --git a/octavia/tests/functional/api/v2/test_listener.py b/octavia/tests/functional/api/v2/test_listener.py
index 793be221b8..533ae0379f 100644
--- a/octavia/tests/functional/api/v2/test_listener.py
+++ b/octavia/tests/functional/api/v2/test_listener.py
@@ -1044,6 +1044,51 @@ class TestListener(base.BaseAPITest):
         self.assertEqual(constants.CLIENT_AUTH_NONE,
                          listener_api.get('client_authentication'))
 
+    def test_create_tls_with_no_subject_no_alt_names(self):
+        tls_cert_mock = mock.MagicMock()
+        tls_cert_mock.get_certificate.return_value = (
+            sample_certs.NOCN_NOSUBALT_CRT)
+        self.cert_manager_mock().get_cert.return_value = tls_cert_mock
+
+        lb_listener = {'name': 'listener1-no-subject-no-alt-names',
+                       'default_pool_id': None,
+                       'description': 'desc1',
+                       'admin_state_up': False,
+                       'protocol': constants.PROTOCOL_TERMINATED_HTTPS,
+                       'protocol_port': 80, 'connection_limit': 10,
+                       'default_tls_container_ref': uuidutils.generate_uuid(),
+                       'insert_headers': {},
+                       'project_id': self.project_id,
+                       'loadbalancer_id': self.lb_id,
+                       'tags': ['test_tag']}
+        body = self._build_body(lb_listener)
+        response = self.post(self.LISTENERS_PATH, body, status=400)
+        self.assertIn("No CN or DNSName", response)
+
+    def test_create_tls_with_no_subject_with_alt_names(self):
+        tls_cert_mock = mock.MagicMock()
+        tls_cert_mock.get_certificate.return_value = (
+            sample_certs.NOCN_SUBALT_CRT)
+        tls_cert_mock.get_private_key.return_value = (
+            sample_certs.NOCN_SUBALT_KEY)
+        tls_cert_mock.get_private_key_passphrase.return_value = None
+        self.cert_manager_mock().get_cert.return_value = tls_cert_mock
+
+        lb_listener = {'name': 'listener1-no-subject',
+                       'default_pool_id': None,
+                       'description': 'desc1',
+                       'admin_state_up': False,
+                       'protocol': constants.PROTOCOL_TERMINATED_HTTPS,
+                       'protocol_port': 80, 'connection_limit': 10,
+                       'default_tls_container_ref': uuidutils.generate_uuid(),
+                       'insert_headers': {},
+                       'project_id': self.project_id,
+                       'loadbalancer_id': self.lb_id,
+                       'tags': ['test_tag']}
+        body = self._build_body(lb_listener)
+        response = self.post(self.LISTENERS_PATH, body, status=201)
+        self.assertIn("PENDING_CREATE", response)
+
     def test_create_with_ca_cert_and_option(self):
         self.cert_manager_mock().get_secret.return_value = (
             sample_certs.X509_CA_CERT)
diff --git a/releasenotes/notes/Handle-blank-cert-subjects-b660d403ce56b0b8.yaml b/releasenotes/notes/Handle-blank-cert-subjects-b660d403ce56b0b8.yaml
new file mode 100644
index 0000000000..bccbd6db6d
--- /dev/null
+++ b/releasenotes/notes/Handle-blank-cert-subjects-b660d403ce56b0b8.yaml
@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Fixed an issue when using certificates with a blank subject or missing CN.