Insufficient response validation in the ldns stub resolver

What FreeBSD says

When used as a stub resolver over UDP, ldns failed to verify that a received response belonged to the outstanding query. It did not check that the response source address and port matched the query destination, that the transaction ID matched, or that the question section of the response matched that of the query.

Impact

Without these checks, an off-path attacker who cannot observe the query can forge UDP responses that ldns will accept as genuine. By injecting spoofed replies, the attacker can return arbitrary DNS data to any program that uses ldns for stub resolving, including drill(1).

Excerpt from the FreeBSD advisory. Read the original for the full text and the fix.