Medium · published July 17, 2026
### Impact
If this library is used in tandem with the `permessage-deflate` extension, a
WebSocket server or client can be made to accept messages that are larger than
the configured maximum message size. This is because this limit is checked
against the message frames' length headers, which give the size of the
compressed data, not the size after decompression. This can lead to applications
accepting larger messages than expected and exceeding their intended resource
usage.
### Patches
The issue has been patched in version 0.8.1, by checking the length of messages
after they are processed by incoming extensions. 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.