diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 5a9802e03e5ddc..e8cf2fc1b10c8a 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -4471,147 +4471,6 @@ os__path_splitroot_impl(PyObject *module, path_t *path)
 
 #endif /* MS_WINDOWS */
 
-
-#ifdef MS_WINDOWS
-
-/* We centralise SECURITY_ATTRIBUTE initialization based around
-templates that will probably mostly match common POSIX mode settings.
-The _Py_SECURITY_ATTRIBUTE_DATA structure contains temporary data, as
-a constructed SECURITY_ATTRIBUTE structure typically refers to memory
-that has to be alive while it's being used.
-
-Typical use will look like:
-    SECURITY_ATTRIBUTES *pSecAttr = NULL;
-    struct _Py_SECURITY_ATTRIBUTE_DATA secAttrData;
-    int error, error2;
-
-    Py_BEGIN_ALLOW_THREADS
-    switch (mode) {
-    case 0x1C0: // 0o700
-        error = initializeMkdir700SecurityAttributes(&pSecAttr, &secAttrData);
-        break;
-    ...
-    default:
-        error = initializeDefaultSecurityAttributes(&pSecAttr, &secAttrData);
-        break;
-    }
-
-    if (!error) {
-        // do operation, passing pSecAttr
-    }
-
-    // Unconditionally clear secAttrData.
-    error2 = clearSecurityAttributes(&pSecAttr, &secAttrData);
-    if (!error) {
-        error = error2;
-    }
-    Py_END_ALLOW_THREADS
-
-    if (error) {
-        PyErr_SetFromWindowsErr(error);
-        return NULL;
-    }
-*/
-
-struct _Py_SECURITY_ATTRIBUTE_DATA {
-    SECURITY_ATTRIBUTES securityAttributes;
-    PACL acl;
-    SECURITY_DESCRIPTOR sd;
-    EXPLICIT_ACCESS_W ea[4];
-    char sid[64];
-};
-
-static int
-initializeDefaultSecurityAttributes(
-    PSECURITY_ATTRIBUTES *securityAttributes,
-    struct _Py_SECURITY_ATTRIBUTE_DATA *data
-) {
-    assert(securityAttributes);
-    assert(data);
-    *securityAttributes = NULL;
-    memset(data, 0, sizeof(*data));
-    return 0;
-}
-
-static int
-initializeMkdir700SecurityAttributes(
-    PSECURITY_ATTRIBUTES *securityAttributes,
-    struct _Py_SECURITY_ATTRIBUTE_DATA *data
-) {
-    assert(securityAttributes);
-    assert(data);
-    *securityAttributes = NULL;
-    memset(data, 0, sizeof(*data));
-
-    if (!InitializeSecurityDescriptor(&data->sd, SECURITY_DESCRIPTOR_REVISION)
-        || !SetSecurityDescriptorGroup(&data->sd, NULL, TRUE)) {
-        return GetLastError();
-    }
-
-    int use_alias = 0;
-    DWORD cbSid = sizeof(data->sid);
-    if (!CreateWellKnownSid(WinCreatorOwnerRightsSid, NULL, (PSID)data->sid, &cbSid)) {
-        use_alias = 1;
-    }
-
-    data->securityAttributes.nLength = sizeof(SECURITY_ATTRIBUTES);
-    data->ea[0].grfAccessPermissions = GENERIC_ALL;
-    data->ea[0].grfAccessMode = SET_ACCESS;
-    data->ea[0].grfInheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;
-    if (use_alias) {
-        data->ea[0].Trustee.TrusteeForm = TRUSTEE_IS_NAME;
-        data->ea[0].Trustee.TrusteeType = TRUSTEE_IS_ALIAS;
-        data->ea[0].Trustee.ptstrName = L"CURRENT_USER";
-    } else {
-        data->ea[0].Trustee.TrusteeForm = TRUSTEE_IS_SID;
-        data->ea[0].Trustee.TrusteeType = TRUSTEE_IS_WELL_KNOWN_GROUP;
-        data->ea[0].Trustee.ptstrName = (LPWCH)(SID*)data->sid;
-    }
-
-    data->ea[1].grfAccessPermissions = GENERIC_ALL;
-    data->ea[1].grfAccessMode = SET_ACCESS;
-    data->ea[1].grfInheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;
-    data->ea[1].Trustee.TrusteeForm = TRUSTEE_IS_NAME;
-    data->ea[1].Trustee.TrusteeType = TRUSTEE_IS_ALIAS;
-    data->ea[1].Trustee.ptstrName = L"SYSTEM";
-
-    data->ea[2].grfAccessPermissions = GENERIC_ALL;
-    data->ea[2].grfAccessMode = SET_ACCESS;
-    data->ea[2].grfInheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;
-    data->ea[2].Trustee.TrusteeForm = TRUSTEE_IS_NAME;
-    data->ea[2].Trustee.TrusteeType = TRUSTEE_IS_ALIAS;
-    data->ea[2].Trustee.ptstrName = L"ADMINISTRATORS";
-
-    int r = SetEntriesInAclW(3, data->ea, NULL, &data->acl);
-    if (r) {
-        return r;
-    }
-    if (!SetSecurityDescriptorDacl(&data->sd, TRUE, data->acl, FALSE)) {
-        return GetLastError();
-    }
-    data->securityAttributes.lpSecurityDescriptor = &data->sd;
-    *securityAttributes = &data->securityAttributes;
-    return 0;
-}
-
-static int
-clearSecurityAttributes(
-    PSECURITY_ATTRIBUTES *securityAttributes,
-    struct _Py_SECURITY_ATTRIBUTE_DATA *data
-) {
-    assert(securityAttributes);
-    assert(data);
-    *securityAttributes = NULL;
-    if (data->acl) {
-        if (LocalFree((void *)data->acl)) {
-            return GetLastError();
-        }
-    }
-    return 0;
-}
-
-#endif
-
 /*[clinic input]
 os.mkdir
 
@@ -4644,8 +4503,8 @@ os_mkdir_impl(PyObject *module, path_t *path, int mode, int dir_fd)
 #ifdef MS_WINDOWS
     int error = 0;
     int pathError = 0;
+    SECURITY_ATTRIBUTES secAttr = { sizeof(secAttr) };
     SECURITY_ATTRIBUTES *pSecAttr = NULL;
-    struct _Py_SECURITY_ATTRIBUTE_DATA secAttrData;
 #endif
 #ifdef HAVE_MKDIRAT
     int mkdirat_unavailable = 0;
@@ -4658,26 +4517,34 @@ os_mkdir_impl(PyObject *module, path_t *path, int mode, int dir_fd)
 
 #ifdef MS_WINDOWS
     Py_BEGIN_ALLOW_THREADS
-    switch (mode) {
-    case 0x1C0: // 0o700
-        error = initializeMkdir700SecurityAttributes(&pSecAttr, &secAttrData);
-        break;
-    default:
-        error = initializeDefaultSecurityAttributes(&pSecAttr, &secAttrData);
-        break;
+    if (mode == 0700 /* 0o700 */) {
+        ULONG sdSize;
+        pSecAttr = &secAttr;
+        // Set a discreationary ACL (D) that is protected (P) and includes
+        // inheritable (OICI) entries that allow (A) full control (FA) to
+        // SYSTEM (SY), Administrators (BA), and the owner (OW).
+        if (!ConvertStringSecurityDescriptorToSecurityDescriptorW(
+            L"D:P(A;OICI;FA;;;SY)(A;OICI;FA;;;BA)(A;OICI;FA;;;OW)",
+            SDDL_REVISION_1,
+            &secAttr.lpSecurityDescriptor,
+            &sdSize
+        )) {
+            error = GetLastError();
+        }
     }
     if (!error) {
         result = CreateDirectoryW(path->wide, pSecAttr);
-        error = clearSecurityAttributes(&pSecAttr, &secAttrData);
-    } else {
-        // Ignore error from "clear" - we have a more interesting one already
-        clearSecurityAttributes(&pSecAttr, &secAttrData);
+        if (secAttr.lpSecurityDescriptor &&
+            // uncommonly, LocalFree returns non-zero on error, but still uses
+            // GetLastError() to see what the error code is
+            LocalFree(secAttr.lpSecurityDescriptor)) {
+            error = GetLastError();
+        }
     }
     Py_END_ALLOW_THREADS
 
     if (error) {
-        PyErr_SetFromWindowsErr(error);
-        return NULL;
+        return PyErr_SetFromWindowsErr(error);
     }
     if (!result) {
         return path_error(path);