websocket-driver: Message corruption via abuse of protocol length headers

Impact

The frame format in draft versions of the WebSocket protocol includes a length header that allows an arbitrarily large integer to be encoded as a sequence of bytes with the high bit set. By sending an indefinite sequence of bytes with values 0x80 or above, a client can make the server parse these bytes into an ever-growing integer. Since JavaScript numbers are 64-bit floating point values, this number will eventually lose precision and lead to the subsequent payload being parsed incorrectly.

Patches

The issue has been patched in version 0.7.5 by rejecting the message if the length header exceeds the configured maximum message length. All users should upgrade to this version.

Workarounds

No known workarounds exist.

Acknowledgements

This issue was discovered and reported by Pranjali Thakur, DepthFirst Security Research Team.