Details of the mechanism...
are sketchy in reports. It's rather "ooh! look, I can fax this picture to you and pwn all your secrets!" rather than "Using a dial-up fax modem, I can cause a buffer overrun on your machine, which is a potential foothold into an exploit of variable effectiveness."
And over-run the buffer into what, exactly? Just because you can cause a particular category of fault or error condition doesn't mean that the error is exploitable. It take a huge leap of the imagination to go from over-running a buffer in image memory to executing very specific coded instructions which will compromise an entire network.
I call this out as 99.999% bullshit attention seeking. Unless it's just the media portraying this as yet another thing to panic about. I expected better from the Reg, though, in terms of technical details.