Description of problem:

fetchctx structures,  not keeping count of its uses, might be read
even after beind deallocated resulting in name server denial of
service under certain circumstances.

Version-Release number of selected component (if applicable):

Unclear whether this issue also affects 3.2 BIND, besides 3.3.
For sure affects FC-5, FC-6 and RHEL-5

How reproducible:

Hardly ever.

Steps to Reproduce:

No known way to reproduce. The advisory notes, that the issue can be
partly mitigated by disabling recursion, so probably some deep recursive
queries might trigger the bug?
  
Actual results:

Server DoS?

Expected results:

What would you expect from read of deallocated memory? :)

Additional info:

ISC sucks at providing either patches or information about the flaws.
The attached patch incorporates another fix which changes roughly the
same code.