26C is 78F, which is fine. That's room temperature around these parts.
The beer will age faster at 26C than say 20C or even 10C, but we're not talking about that much. Every 10C change in temperature speeds up chemical reactions by a factor of 2. So your beer will age about 2.2 times faster at 26C than it would at cellar temperatures. It's not a big deal in the long run.