static PyObject *__pyx_pf_17clickhouse_driver_14bufferedreader_14BufferedReader_2read_into_buffer(CYTHON_UNUSED struct __pyx_obj_17clickhouse_driver_14bufferedreader_BufferedReader *__pyx_v_self) {
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  /* "clickhouse_driver/bufferedreader.pyx":23
 * 
 *     def read_into_buffer(self):
 *         raise NotImplementedError             # <<<<<<<<<<<<<<
 * 
 *     def read(self, Py_ssize_t unread):
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 *     def read_into_buffer(self):             # <<<<<<<<<<<<<<
 *         raise NotImplementedError
 * 
 */

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The program copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow.