Summary
An attacker can cause Denial of Service by sending a specially crafted malicious XML payload (e.g., repeated </ characters) to a Netty server utilizing XmlFrameDecoder, causing the server's EventLoop thread to exhaust CPU resources and become unresponsive.
Details
io.netty.handler.codec.xml.XmlFrameDecoder suffers from a vulnerability resulting in CPU exhaustion. When < followed by / is encountered, the decoder scans the remaining buffer for a closing >.
Because the parser state is not saved between decode() invocations, an attacker can trickle-feed a payload of </ characters. This forces the decoder to repeatedly rescan the entire accumulated buffer. A 1MB maxFrameLength is enough to completely hang a server's thread while it loops endlessly.
Impact
Denial of Service via CPU Exhaustion. Any application utilizing Netty's XmlFrameDecoder is impacted. An unauthenticated remote attacker can exploit this flaw by sending a modest amount of malformed XML data to an exposed port.
References
violetagg Reporter
Summary
An attacker can cause Denial of Service by sending a specially crafted malicious XML payload (e.g., repeated
</characters) to a Netty server utilizing XmlFrameDecoder, causing the server's EventLoop thread to exhaust CPU resources and become unresponsive.Details
io.netty.handler.codec.xml.XmlFrameDecodersuffers from a vulnerability resulting in CPU exhaustion. When<followed by/is encountered, the decoder scans the remaining buffer for a closing>.Because the parser state is not saved between
decode()invocations, an attacker can trickle-feed a payload of</characters. This forces the decoder to repeatedly rescan the entire accumulated buffer. A 1MBmaxFrameLengthis enough to completely hang a server's thread while it loops endlessly.Impact
Denial of Service via CPU Exhaustion. Any application utilizing Netty's XmlFrameDecoder is impacted. An unauthenticated remote attacker can exploit this flaw by sending a modest amount of malformed XML data to an exposed port.
References