What is CVE-2018-10199?

CVE-2018-10199 is a critical-severity vulnerability in Mruby, classified under Use After Free. CVSS score: 9.8/10. Published 2018-04-18.

How severe is CVE-2018-10199?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2018-10199 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Use After Free in Mruby

CVE-2018-10199

In versions of mruby up to and including 1.4.0, a use-after-free vulnerability exists in src/io.c::File#initilialize_copy(). An attacker that can cause Ruby code to be run can possibly use this to execute arbitrary code.

Vulnerability class: Use-After-Free

Published 2018-04-18 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.023 (82.3th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 82nd percentile — 82.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.023 · newest: 0.023 · change: -0.000

Affected products

Mruby

Weakness classification (CWE)

CWE-416 — Use After Free

Public proof-of-concept exploits

nautilus-fuzz/nautilus

References

github.com/mruby/mruby/commit/b51b21fc63c9805862322551387d9036f2b63433 (Patch)
github.com/mruby/mruby/issues/4001 (Third Party Advisory)

Frequently asked questions

What is CVE-2018-10199?: CVE-2018-10199 is a critical-severity vulnerability in Mruby, classified under Use After Free. CVSS score: 9.8/10. Published 2018-04-18.
How severe is CVE-2018-10199?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2018-10199 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.