What is CVE-2018-4391?

CVE-2018-4391 is a medium-severity vulnerability in Apple Iphone OS. CVSS score: 5.5/10. Published 2020-10-27.

How severe is CVE-2018-4391?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Vulnerability in Apple Iphone OS

CVE-2018-4391

An inconsistent user interface issue was addressed with improved state management. This issue is fixed in macOS High Sierra 10.13.1, Security Update 2017-001 Sierra, and Security Update 2017-004 El Capitan, watchOS 4.3, iOS 12.1. Processing a maliciously crafted text message may lead to UI spoofing.

Published 2020-10-27 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.009 (57.0th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 57th percentile — 57.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

References

support.apple.com/en-us/HT209192 (Vendor Advisory)
support.apple.com/en-us/HT208221 (Vendor Advisory)
support.apple.com/en-us/HT208696 (Vendor Advisory)

Frequently asked questions

What is CVE-2018-4391?: CVE-2018-4391 is a medium-severity vulnerability in Apple Iphone OS. CVSS score: 5.5/10. Published 2020-10-27.
How severe is CVE-2018-4391?: Medium severity. CVSS v3 base score is 5.5 out of 10.