eSignal v7 remote buffer overflow (exploit)

Type securityvulns
Reporter Securityvulns
Modified 2004-03-26T00:00:00



===========-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=========== VizibleSoft Security Advisory #2004/01 25th Mar 2004 ===========-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-===========

Product: eSignal 7.6, 7.5 (maybe earlier)

Systems: Windows (all versions)

Problem: Stack-based buffer overflow

Severity: Remote code execution

Risk: High

Product description: ~~~~~~~~~~~~~~~~~~~~ "eSignal is the nation's leading provider of real-time financial and market information. eSignal is a popular platform for institutional and professional traders. eSignal is a market data solution bundled for best value for small to mid-size institutional investors that also includes additional optional services..."

Vulnerability: ~~~~~~~~~~~~~~ eSignal main application "WinSig.exe" listens for incoming data requests on tcp port 80.

While parsing requests, it suffers from classic stack-based buffer overflow, when parameter string is about 1040 characters long:


... bang!

Overflow occurs in Specs.dll and EIP is fully controllable, as the function return address on the stack is completelly overwritten.

Exploitation: ~~~~~~~~~~~~~ Pretty trivial, except that overflow string can not contain NULL-bytes and all lower-case characters are converted to upper-case.

As we overwrite stack with return address and code, we use standard "JMP ESP" technique to direct execution back to us.

"jmp esp" opcode was found in MFC71.dll, which is distributed in eSignal package and loads from program folder, thus making exploit to be eSignal version specific instead of OS (Windoze) specific.

While I was working on advisory, eSignal released v7.6 which is vulnerable as well and even more "overflow-friendly", as previous was compiled with debug bits for ESP value checking at the end of each procedure. But in both cases it's almost similar.

Proof of concept code: ~~~~~~~~~~~~~~~~~~~~~~ Exploit written in Perl, which downloads and executes file from the specified URL available here:

Solution: ~~~~~~~~~ Vendor's technical support ignored my request for company's security contacts. I wasn't surprised, as the most support staff these days is zombified and can't figure out doing something they were not programmed to. Plus, company falls into category of "those who does not care" moneymakers, so after two weeks time I realized there won't be any answer.

Thus, solution is obvious:

Close tcp 80 to outside world with your favorite firewall.

Disclaimer: ~~~~~~~~~~~ The information in this advisory is believed to be true though it may be false. Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties with regard to this information. In no event shall the authors be liable for any damages whatsoever arising out of or in connection with the use or spread of this information. Any use of this information is at the user's own risk.

Legal Notice: ~~~~~~~~~~~~~ This advisory is copyright (c) 2004 You may distribute it unmodified. You may not modify it and distribute it or distribute parts of it without the author's written permission - this especially applies to the so called "vulnerabilities databases" and "security checkers".


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