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Problem
Fuzzing found two reproducible decode-time crashes:
NegativeArraySizeException in ProtocolUtils.readBinaryTag(...) (bubbles up from Adventure NBT parsing).
JsonSyntaxException/MalformedJsonException in LegacyPlayerListItemPacket.readOptionalComponent(...).
These exceptions were unhandled and could crash/abort decode paths instead of failing gracefully.
This vulnerability can be exploited by a DoS attack and this fix will improve code robustness
This vulnerability can be exploited by a DoS attack and this fix will improve code robustness
This path is not exploitable client-side. Both cases where the exceptions are caught are clientbound-only (readBinaryTag() isnt used serverbound). This could only be exploited by a malicious backend server.
readBinaryTag() can throw way more than just the NegativeArraySizeException (most obvious example is an index out of bounds in ProtocolUtils#readBinaryTag line 506; BINARY_TAG_TYPES[buf.readByte()])
The server won't crash anyways as the uncaught exceptions will be caught upstream (MinecraftDecoder#tryDecode), and kill the connection instead of killing/DOSing the proxy
Fuzzing found two reproducible decode-time crashes
Are you able to share the steps to actually reproduce a full on proxy crash by sending some malformed packets from the client?
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Problem
Fuzzing found two reproducible decode-time crashes:
These exceptions were unhandled and could crash/abort decode paths instead of failing gracefully.
This vulnerability can be exploited by a DoS attack and this fix will improve code robustness