diff -up openssl-3.0.1/crypto/ec/ec_lib.c.disable_explicit_ec openssl-3.0.1/crypto/ec/ec_lib.c
--- openssl-3.0.1/crypto/ec/ec_lib.c.disable_explicit_ec	2022-02-22 09:08:48.557823665 +0100
+++ openssl-3.0.1/crypto/ec/ec_lib.c	2022-02-22 09:09:26.634133847 +0100
@@ -1458,7 +1458,7 @@ static EC_GROUP *ec_group_explicit_to_na
                 goto err;
         }
     } else {
-        ret_group = (EC_GROUP *)group;
+        goto err;
     }
     EC_GROUP_free(dup);
     return ret_group;
diff -up openssl-3.0.1/providers/implementations/keymgmt/ec_kmgmt.c.disable_explicit_ec openssl-3.0.1/providers/implementations/keymgmt/ec_kmgmt.c
--- openssl-3.0.1/providers/implementations/keymgmt/ec_kmgmt.c.disable_explicit_ec	2022-02-22 13:04:16.850856612 +0100
+++ openssl-3.0.1/providers/implementations/keymgmt/ec_kmgmt.c	2022-02-22 14:16:19.848369641 +0100
@@ -936,11 +936,8 @@ int ec_validate(const void *keydata, int
     if ((selection & OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS) != 0) {
         int flags = EC_KEY_get_flags(eck);
 
-        if ((flags & EC_FLAG_CHECK_NAMED_GROUP) != 0)
-            ok = ok && EC_GROUP_check_named_curve(EC_KEY_get0_group(eck),
-                           (flags & EC_FLAG_CHECK_NAMED_GROUP_NIST) != 0, ctx);
-        else
-            ok = ok && EC_GROUP_check(EC_KEY_get0_group(eck), ctx);
+        ok = ok && EC_GROUP_check_named_curve(EC_KEY_get0_group(eck),
+                      (flags & EC_FLAG_CHECK_NAMED_GROUP_NIST) != 0, ctx);
     }
 
     if ((selection & OSSL_KEYMGMT_SELECT_PUBLIC_KEY) != 0) {
@@ -1217,6 +1214,10 @@ static int ec_gen_assign_group(EC_KEY *e
         ERR_raise(ERR_LIB_PROV, PROV_R_NO_PARAMETERS_SET);
         return 0;
     }
+    if (EC_GROUP_get_curve_name(group) == NID_undef) {
+        ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_CURVE);
+        return 0;
+    }
     return EC_KEY_set_group(ec, group) > 0;
 }