Impact

Denial of Service.

Attack Steps:

1. The target resolver sends a query
2. The attacker forges a malformed UDP packet with a length of 0 and returns them to the target resolver
3. The target resolver erroneously interprets the 0 length as a graceful shutdown of the connection. (this is only valid for TCP connections, UDP is connection-less)
4. Current resolution fails, DoS attack is achieved.

Patches

Fixed in 1.19.1

Workarounds

No workarounds are available.

Credit

Xiang Li
Network and Information Security Laboratory, Tsinghua University