Unbound 1.21.1 released

We are pleased to announce the release of version 1.21.1 of the Unbound recursive DNS resolver.

This security release fixes CVE-2024-8508.

A vulnerability has been discovered in Unbound when handling replies with very large RRsets that Unbound needs to perform name compression for.

Malicious upstreams responses with very large RRsets can cause Unbound to spend a considerable time applying name compression to downstream replies. This can lead to degraded performance and eventually denial of service in well orchestrated attacks.

Unbound version 1.21.1 introduces a hard limit on the number of name compression calculations it is willing to do per packet. Packets that need more compression will result in semi-compressed packets or truncated packets, even on TCP for huge messages, to avoid locking the CPU for long.

This change should not affect normal DNS traffic.

We would like to thank Toshifumi Sakaguchi for discovering and responsibly disclosing the vulnerability.

For a full list of changes, binary and source packages, see the download page.