Re: Guile security vulnerability w/ listening on localhost + port (with fix)

[Lizzie Dixon <_@lizzie.io>]

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Hi,

On 10/11, Christopher Allan Webber wrote:
> The default in Guile has been to expose a port over localhost to which
> code may be passed.  The assumption for this is that only a local user
> may write to localhost, so it should be safe.  Unfortunately, users
> simultaneously developing Guile and operating modern browsers are
> vulnerable to a combination of an html form protocol attack [1] and a
> DNS rebinding attack [2].  How to combine these attacks is published in
> the article "How to steal any developer's local database" [3].

> 
> In Guile's case, the general idea is that you visit some site which
> presumably loads some javascript code (or tricks the developer into
> pressing a button which performs a POST), and the site operator switches
> the DNS from their own IP to 127.0.0.1.  Then a POST is done from the
> website to 127.0.0.1 with the body containing scheme code.  This code is
> then executed by the Guile interpreter on the listening port.

You don't need to rebind DNS to exploit this bug, or other bugs like
it. I wrote some details here:

<https://blog.lizzie.io/exploiting-CVE-2016-8606.html>

Best,

Lizzie.

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