diff --git a/scripts/mbedtls_dev/generate_server9_bad_saltlen.py b/scripts/mbedtls_dev/generate_server9_bad_saltlen.py
new file mode 100755
index 0000000000..68a8a5f15d
--- /dev/null
+++ b/scripts/mbedtls_dev/generate_server9_bad_saltlen.py
@@ -0,0 +1,100 @@
+#!/usr/bin/env python3
+"""Generate server9-bad-saltlen.crt
+
+`server9-bad-saltlen.crt (announcing saltlen = 0xDE, signed with another len)`. It can not generate
+with normal command. This script is to generate the file.
+"""
+
+# Copyright The Mbed TLS Contributors
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import subprocess
+import argparse
+from asn1crypto import pem, x509, core #type: ignore #pylint: disable=import-error
+
+OPENSSL_RSA_PSS_CERT_COMMAND = r'''
+openssl x509 -req -CA {ca_name}.crt -CAkey {ca_name}.key -set_serial 24 {ca_password} \
+    {openssl_extfile} -days 3650 -outform DER -in {csr}  \
+    -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:{anounce_saltlen} \
+    -sigopt rsa_mgf1_md:sha256
+'''
+SIG_OPT = \
+    r'-sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:{saltlen} -sigopt rsa_mgf1_md:sha256'
+OPENSSL_RSA_PSS_DGST_COMMAND = r'''openssl dgst -sign {ca_name}.key {ca_password} \
+    -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:{actual_saltlen} \
+    -sigopt rsa_mgf1_md:sha256'''
+
+
+def auto_int(x):
+    return int(x, 0)
+
+
+def build_argparser(parser):
+    """Build argument parser"""
+    parser.description = __doc__
+    parser.add_argument('--ca-name', type=str, required=True,
+                        help='Basename of CA files')
+    parser.add_argument('--ca-password', type=str,
+                        required=True, help='CA key file password')
+    parser.add_argument('--csr', type=str, required=True,
+                        help='CSR file for generating certificate')
+    parser.add_argument('--openssl-extfile', type=str,
+                        required=True, help='X905 v3 extension config file')
+    parser.add_argument('--anounce_saltlen', type=auto_int,
+                        required=True, help='Announced salt length')
+    parser.add_argument('--actual_saltlen', type=auto_int,
+                        required=True, help='Actual salt length')
+    parser.add_argument('--output', type=str, required=True)
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    build_argparser(parser)
+    args = parser.parse_args()
+
+    return generate(**vars(args))
+
+def generate(**kwargs):
+    """Generate different slt length certificate file."""
+    ca_password = kwargs.get('ca_password', '')
+    if ca_password:
+        kwargs['ca_password'] = r'-passin "pass:{ca_password}"'.format(
+            **kwargs)
+    else:
+        kwargs['ca_password'] = ''
+    extfile = kwargs.get('openssl_extfile', '')
+    if extfile:
+        kwargs['openssl_extfile'] = '-extfile {openssl_extfile}'.format(
+            **kwargs)
+    else:
+        kwargs['openssl_extfile'] = ''
+
+    cmd = OPENSSL_RSA_PSS_CERT_COMMAND.format(**kwargs)
+    der_bytes = subprocess.check_output(cmd, shell=True)
+    target_certificate = x509.Certificate.load(der_bytes)
+
+    cmd = OPENSSL_RSA_PSS_DGST_COMMAND.format(**kwargs)
+    #pylint: disable=unexpected-keyword-arg
+    der_bytes = subprocess.check_output(cmd,
+                                        input=target_certificate['tbs_certificate'].dump(),
+                                        shell=True)
+
+    with open(kwargs.get('output'), 'wb') as f:
+        target_certificate['signature_value'] = core.OctetBitString(der_bytes)
+        f.write(pem.armor('CERTIFICATE', target_certificate.dump()))
+
+
+if __name__ == '__main__':
+    main()