Wallbleed bug reveals secrets of China's Great Firewallwww.theregister.comBoffins poked around inside censorship engines – here's what they found

The vulnerability itself is triggered by a bug in China's DNS query parser that, under specific conditions, unintentionally returns to the client up to 125 bytes of additional memory data in the forged response. To be more specific, the data is leaked from whatever machine is inspecting the DNS request to potentially block. By carefully crafting a DNS query, you can grab 125 bytes of memory from the censorship middlebox inspecting that query.