facil.io is a C micro-framework for web applications. Prior to commit 5128747363055201d3ecf0e29bf0a961703c9fa0, "fio_json_parse" can enter an infinite loop when it encounters a nested JSON value starting with "i" or "I". The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because "iodine" vendors the same parser code, the issue also affects "iodine" when it parses attacker-controlled JSON. The smallest reproducer I found is "[i". The quoted-value form that originally exposed the issue, "[""i", reaches the same bug because the parser tolerates missing commas and then treats the trailing "i" as the start of another value. Commit 5128747363055201d3ecf0e29bf0a961703c9fa0 fixes the issue.