It looks like some sort of impatiens. I found a French page with some likely candidates, Impatiens balfourii and I. glandulifera, which are identified as aliens to the south Massif Central:

http://causses-cevennes.com/flore/Cevennes.htm

Below is another link, to a page on our native North American impatienses, the jewelweeds.

Here is a link that might be useful: Jewelweed -- pictures, uses, commentary

i think we have a winner!
Impatiens balfourii looks like a dead ringer, cept for the stems wich im sure is a matter of lighting conditions...
thanx alot dude :)