Before JSONata 2.2.0 and 1.8.9, it is possible to craft non-matching inputs to the $toMillis function that cause superlinear backtracking in the ISO-8601 validation regex. This may lead to denial of service in applications that evaluate user-provided JSONata expressions.

This issue has been addressed in JSONata version 2.2.0 or later, and 1.8.9 or later on v1, via fixes that include https://github.com/jsonata-js/jsonata/pull/782 and https://github.com/jsonata-js/jsonata/pull/793. Applications that evaluate user-provided expressions should update ASAP to prevent exploitation.

https://github.com/jsonata-js/jsonata/releases/tag/v2.2.0 https://github.com/jsonata-js/jsonata/releases/tag/v1.8.9

Thank you to Doruk Tan Öztürk for disclosing this issue.