Reachable Assertion in rulex

Impact

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.

Patches

The crashes are fixed in version 0.4.3. Affected users are advised to update to this version.

Workarounds

You can use catch_unwind to recover from panics.

For more information

If you have any questions or comments about this advisory:

• Open an issue in rulex
• Email me at [email protected]

Credits

Credit for finding these bugs goes to

• cargo fuzz and afl.rs
• evanrichter
• ForAllSecure Mayhem