CVE-2026-41146: Boazsegev Facil.io

High severity, CVSS 8.7. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Boazsegev Facil.io: before 5128747363055201d3ecf0e29bf0a961703c9fa0 (fixed in 5128747363055201d3ecf0e29bf0a961703c9fa0)
• Boazsegev Iodine: before 0.7.59 (fixed in 0.7.59)

Published 2026-04-22. Last modified 2026-06-17.