diff --git a/docs/development/test-vectors.rst b/docs/development/test-vectors.rst
index 6f61a7e..4fd358e 100644
--- a/docs/development/test-vectors.rst
+++ b/docs/development/test-vectors.rst
@@ -124,6 +124,8 @@
   "We heart UTF8!™".
 * ``two_basic_constraints.pem`` - An RSA 2048 bit self-signed certificate
   containing two basic constraints extensions.
+* ``two_basic_constraints_csr.pem`` - A cerfificate sigining request
+  for a RSA 2048 bit key containing two basic constraints extensions.
 * ``basic_constraints_not_critical.pem`` - An RSA 2048 bit self-signed
   certificate containing a basic constraints extension that is not marked as
   critical.
@@ -133,9 +135,17 @@
 * ``unsupported_extension.pem`` - An RSA 2048 bit self-signed certificate
   containing an unsupported extension type. The OID was encoded as
   "1.2.3.4" with an ``extnValue`` of "value".
+* ``unsupported_extension_csr.pem`` - A certificate signing request
+  for an RSA 2048 bit key containing containing an unsupported
+  extension type. The OID was encoded as "1.2.3.4" with an
+  ``extnValue`` of "value".
 * ``unsupported_extension_critical.pem`` - An RSA 2048 bit self-signed
   certificate containing an unsupported extension type marked critical. The OID
   was encoded as "1.2.3.4" with an ``extnValue`` of "value".
+* ``unsupported_extension_critical_csr.pem`` - A certificate signing
+  request for an RSA 2048 bit key containing containing an unsupported
+  extension type marked critical. The OID was encoded as "1.2.3.4"
+  with an ``extnValue`` of "value".
 * ``san_email_dns_ip_dirname_uri.pem`` - An RSA 2048 bit self-signed
   certificate containing a subject alternative name extension with the
   following general names: ``rfc822Name``, ``dNSName``, ``iPAddress``,
diff --git a/vectors/cryptography_vectors/x509/custom/two_basic_constraints_csr.pem b/vectors/cryptography_vectors/x509/custom/two_basic_constraints_csr.pem
new file mode 100644
index 0000000..da23c06
--- /dev/null
+++ b/vectors/cryptography_vectors/x509/custom/two_basic_constraints_csr.pem
@@ -0,0 +1,66 @@
+Certificate Request:
+    Data:
+        Version: 2 (0x2)
+        Subject: C=US, ST=Texas, L=Austin, O=PyCA, CN=cryptography.io
+        Subject Public Key Info:
+            Public Key Algorithm: rsaEncryption
+            RSA Public Key: (2048 bit)
+                Modulus (2048 bit):
+                    00:cc:72:54:2d:83:be:73:f5:9a:60:3f:b8:bd:78:
+                    7d:f4:3d:6e:31:38:a9:26:72:86:19:14:87:0d:f4:
+                    68:97:19:2f:d7:7c:80:45:ad:38:27:59:db:57:76:
+                    a5:f3:b1:5e:34:5f:43:63:e5:24:0a:0f:c6:ab:39:
+                    69:d1:1a:87:68:8c:98:02:3a:08:1c:25:d7:65:30:
+                    c3:b6:a9:fa:df:ca:9d:4b:4c:b3:00:a7:fa:ea:de:
+                    ad:99:d2:67:5f:c4:15:0d:b3:70:4d:b2:0a:a7:dd:
+                    35:67:35:b9:4f:a8:b2:f6:a6:22:26:b6:ae:e8:ed:
+                    2d:e7:82:7e:a5:f2:2c:05:d5:03:5a:2e:1e:d0:62:
+                    79:04:55:4b:b3:99:94:8b:9f:6a:5e:ee:6e:b3:d4:
+                    f0:d4:9a:82:ce:e3:f4:81:5c:b2:db:24:85:b8:e4:
+                    1c:6f:a8:3d:4e:91:27:6a:fe:48:29:f2:09:40:9e:
+                    a1:e2:34:41:18:29:ce:f5:24:11:d9:22:2f:6f:94:
+                    cf:22:4e:ba:f2:38:90:00:70:d5:86:d4:6d:c2:ce:
+                    6c:32:74:75:df:f1:1f:c9:a0:be:43:2b:84:34:db:
+                    34:2f:d3:15:8f:ff:85:62:40:79:d3:3c:04:a2:b8:
+                    43:34:ae:c2:3e:1d:ad:c0:4b:28:34:c2:6d:7e:e2:
+                    9f:75
+                Exponent: 65537 (0x10001)
+        Attributes:
+        Requested Extensions:
+            X509v3 Basic Constraints: critical
+                CA:FALSE
+            X509v3 Basic Constraints: critical
+                CA:FALSE
+    Signature Algorithm: sha1WithRSAEncryption
+        b8:00:de:3c:28:bf:56:9a:a7:8f:50:a3:86:a3:02:91:8b:97:
+        1c:b8:73:81:c2:fd:85:d7:6f:ba:b1:c3:18:8a:17:d9:66:cd:
+        b9:9a:9c:1f:c8:0b:88:33:b7:4e:97:b2:60:43:ea:13:57:13:
+        17:7c:23:7d:22:6e:65:b0:0a:bc:dc:12:ec:b3:85:2f:1b:c9:
+        ef:9c:19:f3:15:fd:78:89:a6:d1:2d:b8:bf:b6:17:b8:dc:b5:
+        7a:e6:2a:4d:2c:da:01:10:31:96:12:13:49:08:1b:d9:ba:97:
+        54:e4:21:b8:50:92:9d:1f:30:f0:a2:de:99:8e:da:0e:1f:84:
+        d4:22:2a:f6:d4:3b:43:81:25:ca:2a:e2:17:f6:ef:2f:db:df:
+        67:dc:0f:1b:36:ac:46:b4:39:3b:d6:17:1a:12:fb:5f:1d:28:
+        db:9f:66:38:64:b7:43:ab:84:49:11:3b:ae:f1:30:cf:79:7e:
+        a6:52:ff:91:cb:9c:53:09:44:89:83:cf:04:7b:3c:12:7b:8f:
+        56:e7:48:9a:e5:2a:f3:1f:93:ec:07:5f:1d:f1:6d:59:ed:5e:
+        f6:6a:be:63:60:02:f4:65:34:fb:dc:0a:1b:b3:99:b5:4b:4f:
+        66:55:35:d3:79:85:48:7e:ca:0e:06:0f:92:00:27:93:79:ce:
+        f7:2f:ad:2b
+-----BEGIN CERTIFICATE REQUEST-----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-----END CERTIFICATE REQUEST-----
diff --git a/vectors/cryptography_vectors/x509/custom/unsupported_extension_critical_csr.pem b/vectors/cryptography_vectors/x509/custom/unsupported_extension_critical_csr.pem
new file mode 100644
index 0000000..53ad1fa
--- /dev/null
+++ b/vectors/cryptography_vectors/x509/custom/unsupported_extension_critical_csr.pem
@@ -0,0 +1,64 @@
+Certificate Request:
+    Data:
+        Version: 2 (0x2)
+        Subject: C=US, ST=Texas, L=Austin, O=PyCA, CN=cryptography.io
+        Subject Public Key Info:
+            Public Key Algorithm: rsaEncryption
+            RSA Public Key: (2048 bit)
+                Modulus (2048 bit):
+                    00:e0:ca:5f:ec:b5:1b:cc:8b:32:41:a9:85:ac:bd:
+                    9f:34:0a:eb:c0:a0:74:74:74:7c:f5:ad:84:c4:0b:
+                    7e:e0:08:fe:90:f3:0e:94:d9:4a:47:9d:65:df:c0:
+                    28:4e:ec:25:43:b2:af:b6:5e:f2:fe:de:3e:48:9e:
+                    5c:77:67:fa:f9:ff:68:ee:6f:93:45:28:b6:f8:64:
+                    98:05:37:92:d1:96:55:f2:49:15:03:31:00:c3:8d:
+                    d4:9e:88:b7:d3:81:e3:8d:c1:10:5e:57:87:db:4f:
+                    ba:b4:c9:1c:9f:b7:e7:5a:78:0d:b0:0f:b5:b3:72:
+                    bf:61:4d:ca:99:fc:53:e7:54:3d:35:c4:93:6b:ad:
+                    2b:37:75:46:89:3e:20:b3:6b:16:74:d4:c6:bd:a6:
+                    84:16:4f:45:3c:c4:9a:ce:31:76:63:32:14:6f:d1:
+                    6c:0c:95:dc:01:ca:37:67:77:d6:b8:5b:c4:5a:4c:
+                    3a:48:6c:85:4b:e5:78:7f:35:aa:fa:e0:60:ab:17:
+                    de:87:31:49:66:35:aa:0b:7f:06:35:7d:c7:1c:66:
+                    8a:20:d7:b1:79:38:53:88:cd:27:67:fa:14:81:64:
+                    8c:8e:92:2e:08:1d:5b:28:52:30:87:42:93:d3:f3:
+                    f6:e6:cd:d4:a4:a8:fb:fd:51:6b:1b:a1:ed:a3:c1:
+                    a4:0b
+                Exponent: 65537 (0x10001)
+        Attributes:
+        Requested Extensions:
+            1.2.3.4: 
+                value
+    Signature Algorithm: sha1WithRSAEncryption
+        38:bd:c2:b8:c9:8d:23:e9:b6:aa:fe:dc:43:45:8f:2d:ec:d1:
+        90:be:fa:a6:4e:78:d4:29:90:c4:dd:f9:a4:6c:e9:1a:2b:e7:
+        f9:54:6e:35:ef:a0:11:e3:32:b4:d8:e9:bb:d8:a1:bc:9a:6f:
+        09:87:a0:eb:80:6f:55:63:1f:81:ec:fc:a9:66:4c:13:71:32:
+        f9:a0:1b:b5:70:28:d6:94:57:41:66:3a:48:78:df:e6:fe:ae:
+        1d:64:01:5a:bb:17:f3:77:ed:d2:91:d1:69:f8:ac:51:89:d9:
+        5a:54:fd:25:f5:64:89:bc:9b:c6:66:04:96:05:f9:fc:42:ad:
+        e6:f5:e9:e0:af:ec:6e:20:50:55:73:3d:a4:42:4e:4a:05:b6:
+        77:e8:72:03:1e:7d:ac:7f:19:c3:82:11:0b:54:56:17:f8:a8:
+        18:86:c2:ee:dc:84:68:18:9d:3f:dc:ab:78:08:2a:84:4b:bb:
+        0a:ac:0d:7c:91:c9:8c:7e:1c:46:1f:e2:99:36:be:7a:1f:55:
+        75:b5:5e:fa:d5:b0:b1:73:e2:e7:5f:dc:0c:8a:37:8d:fd:69:
+        1b:24:35:12:f6:45:02:71:bd:13:f6:bd:27:c7:aa:e5:39:bf:
+        e0:20:9b:87:c0:32:e7:94:06:6c:06:2a:e0:6f:df:61:b3:06:
+        8b:1b:3a:93
+-----BEGIN CERTIFICATE REQUEST-----
+MIICuzCCAaMCAQIwVzELMAkGA1UEBhMCVVMxDjAMBgNVBAgMBVRleGFzMQ8wDQYD
+VQQHDAZBdXN0aW4xDTALBgNVBAoMBFB5Q0ExGDAWBgNVBAMMD2NyeXB0b2dyYXBo
+eS5pbzCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAODKX+y1G8yLMkGp
+hay9nzQK68CgdHR0fPWthMQLfuAI/pDzDpTZSkedZd/AKE7sJUOyr7Ze8v7ePkie
+XHdn+vn/aO5vk0UotvhkmAU3ktGWVfJJFQMxAMON1J6It9OB443BEF5Xh9tPurTJ
+HJ+351p4DbAPtbNyv2FNypn8U+dUPTXEk2utKzd1Rok+ILNrFnTUxr2mhBZPRTzE
+ms4xdmMyFG/RbAyV3AHKN2d31rhbxFpMOkhshUvleH81qvrgYKsX3ocxSWY1qgt/
+BjV9xxxmiiDXsXk4U4jNJ2f6FIFkjI6SLggdWyhSMIdCk9Pz9ubN1KSo+/1Raxuh
+7aPBpAsCAwEAAaAfMB0GCSqGSIb3DQEJDjEQMA4wDAYDKgMEBAV2YWx1ZTANBgkq
+hkiG9w0BAQUFAAOCAQEAOL3CuMmNI+m2qv7cQ0WPLezRkL76pk541CmQxN35pGzp
+Givn+VRuNe+gEeMytNjpu9ihvJpvCYeg64BvVWMfgez8qWZME3Ey+aAbtXAo1pRX
+QWY6SHjf5v6uHWQBWrsX83ft0pHRafisUYnZWlT9JfVkibybxmYElgX5/EKt5vXp
+4K/sbiBQVXM9pEJOSgW2d+hyAx59rH8Zw4IRC1RWF/ioGIbC7tyEaBidP9yreAgq
+hEu7CqwNfJHJjH4cRh/imTa+eh9VdbVe+tWwsXPi51/cDIo3jf1pGyQ1EvZFAnG9
+E/a9J8eq5Tm/4CCbh8Ay55QGbAYq4G/fYbMGixs6kw==
+-----END CERTIFICATE REQUEST-----
diff --git a/vectors/cryptography_vectors/x509/custom/unsupported_extension_csr.pem b/vectors/cryptography_vectors/x509/custom/unsupported_extension_csr.pem
new file mode 100644
index 0000000..d96097c
--- /dev/null
+++ b/vectors/cryptography_vectors/x509/custom/unsupported_extension_csr.pem
@@ -0,0 +1,64 @@
+Certificate Request:
+    Data:
+        Version: 2 (0x2)
+        Subject: C=US, ST=Texas, L=Austin, O=PyCA, CN=cryptography.io
+        Subject Public Key Info:
+            Public Key Algorithm: rsaEncryption
+            RSA Public Key: (2048 bit)
+                Modulus (2048 bit):
+                    00:b6:64:25:bd:fc:ba:bf:7b:ee:da:a6:25:79:75:
+                    59:59:cb:bc:da:eb:22:66:97:93:4d:f0:67:39:45:
+                    01:5c:58:0a:17:88:e4:05:14:c8:3f:33:39:5f:a0:
+                    ca:fc:dd:28:3e:b1:d1:0d:87:c1:65:22:21:d3:4a:
+                    5c:f0:b6:4f:49:83:90:b1:88:47:b5:7f:7e:4f:34:
+                    ae:51:a5:ee:fb:92:68:2d:0f:83:86:cb:8e:e7:1d:
+                    ba:f4:6a:f2:ab:81:aa:fc:a4:05:fd:fd:07:88:59:
+                    6a:b7:c7:f5:df:92:e6:fd:ec:e7:a7:6f:ac:02:95:
+                    b7:3f:01:39:82:8e:94:84:18:cf:07:1b:25:5e:94:
+                    56:ec:2e:b7:37:71:ba:09:d2:ef:a3:46:ec:38:34:
+                    1d:0f:f8:d1:1f:4f:11:bd:03:9e:c9:46:65:f7:6d:
+                    80:2d:32:5e:44:6f:e3:21:ec:c2:76:32:62:c2:9e:
+                    47:03:27:8b:ba:49:01:2b:61:1f:6d:7b:3c:05:11:
+                    84:bd:a8:bd:44:e2:30:1e:c2:19:fc:9c:60:79:29:
+                    b9:62:92:97:94:d2:f7:30:84:b6:51:af:f1:9a:61:
+                    80:2e:f8:94:22:f7:73:32:20:79:b1:bf:ea:2d:20:
+                    20:48:51:3d:f1:51:03:b1:02:90:74:46:cf:3b:4e:
+                    f8:4b
+                Exponent: 65537 (0x10001)
+        Attributes:
+        Requested Extensions:
+            1.2.3.4: 
+                value
+    Signature Algorithm: sha1WithRSAEncryption
+        16:5f:86:90:13:fd:63:e6:c9:ca:74:68:b4:6e:e6:c5:c3:46:
+        c1:26:bc:64:2b:fc:ef:be:ab:eb:8b:a9:de:8d:4e:a8:f9:f0:
+        3e:b0:0b:8c:e4:f8:0b:28:5b:13:0c:46:f8:3b:55:cb:cc:cb:
+        ed:6a:4f:16:3a:4b:e9:65:2d:3c:1a:a5:1f:a8:07:ab:22:ee:
+        91:60:f1:06:76:0c:6e:8f:7b:25:36:4b:d6:60:04:77:e6:35:
+        10:4f:eb:fc:2a:c3:71:e5:cb:9f:94:bd:6c:44:08:79:fb:b2:
+        a0:f5:f2:c0:79:b0:c4:22:ec:81:29:b3:97:e5:2f:1f:47:c5:
+        1a:3f:be:50:c8:f4:29:9a:94:1d:19:a9:e2:d6:06:ca:07:43:
+        6c:f1:e4:7e:fb:b8:70:0c:5b:41:c4:10:84:29:39:49:17:09:
+        d1:21:89:d7:c8:e5:6c:48:66:98:ac:8b:33:ab:da:1f:51:a9:
+        2f:4c:39:6d:48:d9:7b:34:7f:b5:1e:9e:b8:87:8b:21:13:41:
+        d4:53:64:c1:16:e0:a8:c1:6f:dc:be:8f:67:ad:e6:30:79:af:
+        bf:7e:ff:64:99:50:d8:4c:58:66:9c:da:d1:53:06:2e:d3:82:
+        e3:2d:b3:65:71:6e:6a:67:cf:e1:96:4f:f7:ac:0b:2e:6e:28:
+        a4:df:f5:e6
+-----BEGIN CERTIFICATE REQUEST-----
+MIICuzCCAaMCAQIwVzELMAkGA1UEBhMCVVMxDjAMBgNVBAgMBVRleGFzMQ8wDQYD
+VQQHDAZBdXN0aW4xDTALBgNVBAoMBFB5Q0ExGDAWBgNVBAMMD2NyeXB0b2dyYXBo
+eS5pbzCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBALZkJb38ur977tqm
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+9d+S5v3s56dvrAKVtz8BOYKOlIQYzwcbJV6UVuwutzdxugnS76NG7Dg0HQ/40R9P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+-----END CERTIFICATE REQUEST-----