---
title: "CVE-2018-5174\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-2018-5174?format=md
keywords: index, follow
---

# CVE-2018-5174

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

**7.5 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2018-5174?format=md#impact-score)

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## Description

In the Windows 10 April 2018 Update, Windows Defender SmartScreen honors
the "SEE\_MASK\_FLAG\_NO\_UI" flag associated with downloaded files and will
not show any UI. Files that are unknown and potentially dangerous will be
allowed to run because SmartScreen will not prompt the user for a decision,
and if the user is offline all files will be allowed to be opened because
Windows won't prompt the user to ask what to do. Firefox incorrectly sets
this flag when downloading files, leading to less secure behavior from
SmartScreen. Note: this issue only affects Windows 10 users running the
April 2018 update or later. It does not affect other Windows users or other
operating systems. This vulnerability affects Thunderbird < 52.8,
Thunderbird ESR < 52.8, Firefox < 60, and Firefox ESR < 52.8.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2018-5174?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| firefox | 18.04 LTS bionic | Not affected |
| 17.10 artful | Not affected |
| 16.04 LTS xenial | Not affected |
| 14.04 LTS trusty | Not in release |
| thunderbird | 18.04 LTS bionic | Not affected |
| 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)

Windows only

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

7.5 · High

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 7.5 · High |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-5174)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2018-5174)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2018-5174)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2018-5174)

### Other references

* <https://www.mozilla.org/en-US/security/advisories/mfsa2018-11/#CVE-2018-5174>
* <https://www.mozilla.org/en-US/security/advisories/mfsa2018-13/#CVE-2018-5174>
* <https://www.cve.org/CVERecord?id=CVE-2018-5174>