What is CVE-2018-5138?

CVE-2018-5138 is a medium-severity vulnerability in Google Android, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2018-06-11.

How severe is CVE-2018-5138?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Improper input validation in Google Android

CVE-2018-5138

A spoofing vulnerability can occur when a malicious site with an extremely long domain name is opened in an Android Custom Tab (a browser panel inside another app) and the default browser is Firefox for Android. This could allow an attacker to spoof which page is actually loaded and in use. Note: this issue only affects Firefox for Android. Other versions and operating systems are unaffected. This vulnerability affects Firefox < 59.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2018-06-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.011 (64.8th percentile), scored 2026-10-04.

Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 64.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: 0.000

Affected products

Google Android
Mozilla Firefox — versions unspecified

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

www.securityfocus.com/bid/103386 (VDB Entry, Third Party Advisory, vdb-entry)
bugzilla.mozilla.org/show_bug.cgi (Issue Tracking, Vendor Advisory)
www.securitytracker.com/id/1040514 (VDB Entry, Third Party Advisory, vdb-entry)
www.mozilla.org/security/advisories/mfsa2018-06/ (Vendor Advisory)

Frequently asked questions

What is CVE-2018-5138?: CVE-2018-5138 is a medium-severity vulnerability in Google Android, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2018-06-11.
How severe is CVE-2018-5138?: Medium severity. CVSS v3 base score is 5.3 out of 10.