You're receiving this bug because the package in Summary has produced _FORTIFY_SOURCE related warnings indicating the presence of a sure overflow in a static buffer.
Even though this is not always an indication of a security problem it might even be. So please check this out ASAP.
By the way, _FORTIFY_SOURCE is disabled when you disable optimisation, so don't try finding out the cause using -O0.
Your friendly neighborhood tinderboxer
Created attachment 250657 [details]
*** Bug 336794 has been marked as a duplicate of this bug. ***
+*vienna-rna-1.8.4-r2 (15 Oct 2010)
+ 15 Oct 2010; Kacper Kowalik <email@example.com>
+ -files/vienna-rna-1.7.2-gcc4.4.patch, -vienna-rna-1.8.4.ebuild,
+ +vienna-rna-1.8.4-r2.ebuild, +files/vienna-rna-1.8.4-implicits.patch,
+ Fix buffer overflows wrt bug 341089. Thanks to Diego for the report. Fix
+ implicit function declarations. Drop old.