CVE-2022-31100: Reachable Assertion in rulex

When parsing untrusted rulex expressions, rulex may crash, possibly enabling a Denial of Service attack. This happens when the expression contains a multi-byte UTF-8 code point in a string literal or after a backslash, because rulex tries to slice into the code point and panics as a result.

This is a security concern for you, if

• your service parses untrusted rulex expressions (expressions provided by an untrusted user), and
• your service becomes unavailable when the thread running rulex panics.