Full Disclosure mailing list archives
Using data: URLs for malware injection
From: Michael Holzt <kju-fd () fqdn org>
Date: Tue, 11 Jan 2005 22:41:41 +0100
Using data: URL for malware injection 2005/01/11, Michael Holzt, kju -at- fqdn.org based on work done by Darren Bounds (see text) As described by Darren Bounds in an earlier posting [1], RFC2397 allows to embed data into an HTML formatted document. While Darren only used this for malicious images, i made some further research which shows that this can also be used to embed an executable file into the document. As shown by Darren, such embedded data is not detected by current AV gateways. This could be abused by websites (and probably HTML email too) for distributing malware. The attack works by using an URL scheme like this: <a href="data:application/x-msdos-program;base64, [base64 data]">Click me!</a> I've made an example available which embeds putty.exe. The example is about 500 kByte HTML and is available on http://kju.de/misc/putty.html. Please do not spread this URL outside of this list because of the traffic. Feel free to copy the example to your own webspace. My tests with various windows based webbrowsers had the following results: - IE6 clicking on the link does nothing - Mozilla 1.5.4 will try to open the "what should i do with that" file dialog and then hangs. needs to get killed. - Firefox 1.0 allows saving of the data to harddisk (on linux it will also display much rubbish in the save dialog) - Opera 7.5.4 tells that it will open the file with notepad (which sounds ok), but will then EXECUTE IT INSTEAD (without further warning). The behaviour of Opera 7.5.4 seems like a major security bug to me. Can someone else confirm this behaviour? References: [1] Posting by Darren Bounds on 2005/01/10, <F873C22A-633A-11D9-97DC-000A95820F5E () intrusense com> http://lists.netsys.com/pipermail/full-disclosure/2005-January/030724.html _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
Current thread:
- Using data: URLs for malware injection Michael Holzt (Jan 11)
- Re: Using data: URLs for malware injection Rafel Ivgi (Jan 12)
- <Possible follow-ups>
- Re: Using data: URLs for malware injection Michael Holzt (Jan 12)