How severe is CVE-2026-41146?

CVE-2026-41146 has a CVSS 4.0 base score of 8.7, rated high severity.

Is CVE-2026-41146 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-41146?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-41146 have an EU (EUVD) identifier?

Yes. CVE-2026-41146 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24583.

When was CVE-2026-41146 published?

CVE-2026-41146 was published on 2026-04-22 and last updated on 2026-06-17.

CVE-2026-41146

CVE-2026-41146 is a high-severity vulnerability with a CVSS 4.0 base score of 8.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: High (CVSS 4.0 base score 8.7)
EPSS exploit prediction: 0% (21st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-24583
Weakness: CWE-400
Published: 2026-04-22
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2026-41146?: 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.
How severe is CVE-2026-41146?: CVE-2026-41146 has a CVSS 4.0 base score of 8.7, rated high severity.
Is CVE-2026-41146 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-41146?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-41146 have an EU (EUVD) identifier?: Yes. CVE-2026-41146 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24583.
When was CVE-2026-41146 published?: CVE-2026-41146 was published on 2026-04-22 and last updated on 2026-06-17.

References

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