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Tftpd32 Client Side Format String Vulnerability
From: "Rustein, Fara Denise (LATCO - Buenos Aires)" <frustein () DELOITTE com>
Date: Tue, 3 Dec 2013 14:16:36 +0000

"Tftpd32 Client Side Format String Vulnerability"

- CVE: CVE-2013-6809
- For reference:
  + "CWE-134: Uncontrolled Format String" - http://cwe.mitre.org/data/definitions/134.html
  + "CAPEC-135: Format String Injection" - http://capec.mitre.org/data/definitions/135.html 

- Affected Vendor: Tftpd32
- Affected System: Tftpd32 v4.00 Build May
- Vendor Disclosure Date: November 16th, 2013
- Public Disclosure Date: December, 1st, 2013
- Vulnerability Status: Fixed

- Description: There is a format string vulnerability on the Tftpd32 software. When the Tftpd server returns a string 
containing a specific format, the Tftpd32 client processes this string and displays it in an error message, triggering 
the vulnerability. This may be leveraged to perform remote command execution and denial of service attacks.
- PoC (1):
  +  The format string used in the "Remote File" field is: %p%p%p%p
  +  The error message displays the processed string: 771C2D8B7672655373207265737706F74
- PoC (2):
  +  The format string used in the "Remote File" field is: %2525wi
  +  Observe that the application crashes.

- Fix: v4.50 release - (http://tftpd32.jounin.net/tftpd32_download.html)
  + http://tftpd32.jounin.net/download/tftpd32.450.zip
  + http://tftpd32.jounin.net/download/Tftpd32-4.50-setup.exe
  + http://tftpd32.jounin.net/download/Tftpd32_SE-4.50-setup.exe
  + http://tftpd32.jounin.net/download/tftpd64.450.zip
  + http://tftpd32.jounin.net/download/Tftpd64-4.50-setup.exe
  + http://tftpd32.jounin.net/download/Tftpd64_SE-4.50-setup.exe
  + http://tftpd32.jounin.net/download/tftpd32-sources.450.zip

- Related Links: Deloitte Argentina - www.deloitte.com/ar
- Credits: This vulnerability was found by Fara Rustein from Deloitte Argentina (https://twitter.com/FaraRustein).
- Feedback: If you have any questions, comments, concerns, updates or suggestions please feel free to send them to: 
frustein () deloitte com

Fara Rustein | Senior Consultant
Cyber Security - Deloitte
The key is searching. Vs nfv zphz qsui ghzf zg xhv yvzqy gj tiwap.

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