Well, Secunia do say that they are a clearing house for security adversies from all over the place so its not really surprising that they probably took the advisory from the PuTTY home page.

As for the Core advisory being a little incoherent, I'm not surprised given their track record on writing stuff which I've seen on FD and other places!

The Core advisory is now up (CORE-2004-0705), in case you're interested. Also I've published my own writeups of the two issues: vuln-modpow and vuln-ssh1-kex. I've mailed those links to both Core and Secunia, so with any luck they can issue revised versions of their advisories that actually say something useful.