An unauthenticated client can drain the RTSP server's packet pool with a couple of dozen requests that carry a Session header the parser cannot convert. The Session branch returns the raw NetX error code instead of an RTSP status c…

Overview

An unauthenticated client can drain the RTSP server's packet pool with a couple of dozen requests

that carry a Session header the parser cannot convert.

The Session branch returns the raw NetX error code instead of an RTSP status code:

/* addons/rtsp/nx_rtsp_server.c:2754 */



status = _nx_utility_string_to_uint(field_value_ptr, field_value_length, &session_id);



if (status)



{

    return(status);      /* NX_INVALID_PARAMETERS / NX_SIZE_ERROR / NX_OVERFLOW */


}

Every other branch of the same function maps its failure to an RTSP status first. The CSeq branch

eighteen lines earlier does exactly that (line 2736 returns NX_RTSP_STATUS_CODE_BAD_REQUEST). The

raw code then reaches _nx_rtsp_server_error_response_send (nx_rtsp_server.c:1234), which does not

recognise it, takes a path that returns without releasing the response packet it already allocated,

and the block never goes back to the pool.

Six requests with an empty Session header against a 22 packet pool:

valid requests:      after request 6: pool available = 21,  AFTER = 22 / 22



malformed requests:  after request 6: pool available = 16,  AFTER = 17 / 22

One block per request, not returned when the client disconnects. Twenty six requests take the pool

to zero and the server starts failing allocations, after which it serves nobody. If the pool is

shared with the rest of the application, as it is in the shipped sample, the rest of the stack

stops with it.

Convert the _nx_utility_string_to_uint failure in the Session branch into

NX_RTSP_STATUS_CODE_BAD_REQUEST the way the CSeq branch does, and release the response packet on

every exit path of _nx_rtsp_server_error_response_send.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.