One protocol level vulnerability that @1440000bytes found recently is https://github.com/joinmarket-ng/joinmarket-ng/issues/577

Summary: the directory nodes don't authenticate peer nicks, so peers can impersonate others and steal their connection. For example by updating the onion to their one and by being the newest connection with that nick and getting their messages. Important messages are encrypted, but the impact of "eclipsing" other makers is relevant. No loss of funds, but yes denial of service.

The fix required a protocol fix, that involves makers and directory nodes. My signet directory node is updated with the fix. Directory node runners on mainnet are encouraged to update.

The fix is only for jm-ng, but backwards compatible. So old directories and makers keep working, but are vulnerable to the attack. Good thing is that new directories still benefit old peers by not allowing new connections to steal their nick. But this is not a strong protection.

The full details are at https://github.com/joinmarket-ng/joinmarket-ng/issues/577

And the protocol improvement proposal is at https://github.com/joinmarket-ng/jmp/blob/main/jmp-0005.md

Thanks to floppy for finding it and to waxwing for helping us understand the issue and design the fix.