---
title: "CVE-2018-5138\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2018-5138?format=md
keywords: index, follow
---

# CVE-2018-5138

Publication date 11 June 2018

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**5.3 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2018-5138?format=md#impact-score)

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## Description

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.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2018-5138?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| firefox | 17.10 artful | Not affected |
| 16.04 LTS xenial | Not affected |
| 14.04 LTS trusty | Not in release |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Notes

---

### [chrisccoulson](https://launchpad.net/~chrisccoulson)

Firefox for Android only

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

5.3 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Privileges required | None |
  | User interaction | None |
  | Scope | Unchanged |
  | Confidentiality impact | None |
  | Integrity impact | Low |
  | Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 5.3 · Medium |
  | Exploitability score | - |
  | Impact score | - |

**Vector:** CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-5138)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2018-5138)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2018-5138)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2018-5138)

### Other references

* <https://www.mozilla.org/en-US/security/advisories/mfsa2018-06/>
* <https://www.cve.org/CVERecord?id=CVE-2018-5138>