Crass: Non-ASCII characters cause superlinear CPU consumption

Impact

When parsing an input containing non-ASCII characters, inefficiencies in how Crass tracks the positions of multi-byte characters result in superlinear parsing time. An attacker-controlled input consisting of many non-ASCII characters could cause excessive CPU consumption and potentially denial of service.

Patches

This is fixed in Crass 1.0.7.

Workarounds

Avoid passing non-ASCII input to Crass. Or cultivate patience.