PT-2026-34238 · Boazsegev · Facil.Io+1

Published 2026-04-22 · Updated 2026-04-22 · CVE-2026-41146

Mitre

CVSS v4.0

8.7

High

AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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.

Fix

Resource Exhaustion

Infinite Loop

Weakness Enumeration

CWE-400

CWE-835

Related Identifiers

CVE-2026-41146

Affected Products

Facil.Io

Iodine

References · 3

• https://nvd.nist.gov/vuln/detail/CVE-2026-41146 · Security Note
• https://github.com/boazsegev/facil.io/commit/5128747363055201d3ecf0e29bf0a961703c9fa0 · Note
• https://github.com/boazsegev/facil.io/security/advisories/GHSA-2x79-gwq3-vxxm · Note