CVE-2018-5174 — Mozilla: Windows Defender SmartScreen UI runs with less secure behavior for downloaded files in Windows 10 April 2018 Update

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HIGH

Mozilla: Windows Defender SmartScreen UI runs with less secure behavior for downloaded files in Windows 10 April 2018 Update

Published Jun 11, 2018

7.5

HIGH

CVSS 3.0

EPSS 1.85%

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.

Affected products

Vendor Mozilla Product Firefox Default
n/a
- Version
  unspecified
  Status
  affected
  Constraints
  <60
Vendor Mozilla Product Firefox ESR Default
n/a
- Version
  unspecified
  Status
  affected
  Constraints
  <52.8
Vendor Mozilla Product Thunderbird Default
n/a
- Version
  unspecified
  Status
  affected
  Constraints
  <52.8
Vendor Mozilla Product Thunderbird ESR Default
n/a
- Version
  unspecified
  Status
  affected
  Constraints
  <52.8

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor

Product

Default status

Versions

Mozilla

Firefox

n/a

Version	Status	Constraints
unspecified	affected	<60

Mozilla

Firefox ESR

n/a

Version	Status	Constraints
unspecified	affected	<52.8

Mozilla

Thunderbird

n/a

Version	Status	Constraints
unspecified	affected	<52.8

Mozilla

Thunderbird ESR

n/a

Version	Status	Constraints
unspecified	affected	<52.8

Red Hat Enterprise Linux 6

firefox

Not affected
Red Hat Enterprise Linux 6

thunderbird

Not affected
Red Hat Enterprise Linux 7

firefox

Not affected
Red Hat Enterprise Linux 7

thunderbird

Not affected

Product	Package	State	Advisory
Red Hat Enterprise Linux 6	firefox	Not affected	n/a
Red Hat Enterprise Linux 6	thunderbird	Not affected	n/a
Red Hat Enterprise Linux 7	firefox	Not affected	n/a
Red Hat Enterprise Linux 7	thunderbird	Not affected	n/a

Remediation

No remediation recorded yet.

Metrics

1.85% 0.01847

Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.

EPSS probability 0.01847

Score over time

2021–2026

EPSS v1
EPSS v2
EPSS v3
EPSS v4
EPSS v5

Percentile over time

EPSS v1
EPSS v2
EPSS v3
EPSS v4
EPSS v5

Table of values (22 key points)

Flat stretches are collapsed; showing up to 120 newest points.

Date	Score	Percentile	Model
Oct 1, 2026	1.85% (0.01847)	78.29th	v5 (v2026.06.15)
Jun 15, 2026	1.87% (0.01871)	76.55th	v5 (v2026.06.15)
Mar 30, 2025	0.56% (0.00561)	65.66th	v4 (v2025.03.14)
Mar 29, 2025	1.84% (0.01837)	71.83th	v4 (v2025.03.14)
Mar 17, 2025	0.62% (0.00618)	68.18th	v4 (v2025.03.14)
Dec 12, 2024	0.55% (0.00545)	78.15th	v3 (v2023.03.01)
Feb 29, 2024	0.55% (0.00545)	76.82th	v3 (v2023.03.01)
Dec 12, 2023	0.55% (0.00545)	74.80th	v3 (v2023.03.01)
Nov 2, 2023	0.59% (0.00589)	75.90th	v3 (v2023.03.01)
Jul 10, 2023	0.66% (0.00662)	76.87th	v3 (v2023.03.01)
Jul 8, 2023	0.68% (0.00677)	77.20th	v3 (v2023.03.01)
Jun 5, 2023	1.02% (0.01022)	81.65th	v3 (v2023.03.01)
May 8, 2023	1.14% (0.01140)	82.60th	v3 (v2023.03.01)
Mar 7, 2023	0.76% (0.00756)	78.16th	v3 (v2023.03.01)
Mar 6, 2023	1.11% (0.01108)	55.18th	v2 (v2022.01.01)
Sep 17, 2022	1.11% (0.01108)	53.57th	v2 (v2022.01.01)
Apr 1, 2022	1.11% (0.01108)	51.54th	v2 (v2022.01.01)
Feb 4, 2022	1.11% (0.01108)	29.61th	v2 (v2022.01.01)
Feb 3, 2022	14.43% (0.14429)	89.66th	v1
Jan 6, 2022	14.43% (0.14429)	89.55th	v1
Sep 1, 2021	14.43% (0.14429)	96.99th	v1
Apr 14, 2021	14.43% (0.14429)	0.00th	v1

Weaknesses (1)

CWE-451

References (11)

http://www.securityfocus.com/bid/104136
vdb-entryx_refsource_BIDThird Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1040896
vdb-entryx_refsource_SECTRACKThird Party AdvisoryVDB Entry
https://access.redhat.com/security/cve/CVE-2018-5174
Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1447080
x_refsource_CONFIRMIssue TrackingPermissions RequiredThird Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1576274
Issue Tracking
https://nvd.nist.gov/vuln/detail/CVE-2018-5174
https://www.cve.org/CVERecord?id=CVE-2018-5174
https://www.mozilla.org/en-US/security/advisories/mfsa2018-11/#CVE-2018-5174
https://www.mozilla.org/security/advisories/mfsa2018-11/
x_refsource_CONFIRMVendor Advisory
https://www.mozilla.org/security/advisories/mfsa2018-12/
x_refsource_CONFIRMVendor Advisory
https://www.mozilla.org/security/advisories/mfsa2018-13/
x_refsource_CONFIRMVendor Advisory

Link	Providers	Tags
http://www.securityfocus.com/bid/104136		vdb-entryx_refsource_BIDThird Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1040896		vdb-entryx_refsource_SECTRACKThird Party AdvisoryVDB Entry
https://access.redhat.com/security/cve/CVE-2018-5174		Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1447080		x_refsource_CONFIRMIssue TrackingPermissions RequiredThird Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1576274		Issue Tracking
https://nvd.nist.gov/vuln/detail/CVE-2018-5174
https://www.cve.org/CVERecord?id=CVE-2018-5174
https://www.mozilla.org/en-US/security/advisories/mfsa2018-11/#CVE-2018-5174
https://www.mozilla.org/security/advisories/mfsa2018-11/		x_refsource_CONFIRMVendor Advisory
https://www.mozilla.org/security/advisories/mfsa2018-12/		x_refsource_CONFIRMVendor Advisory
https://www.mozilla.org/security/advisories/mfsa2018-13/		x_refsource_CONFIRMVendor Advisory

Change history (0)

No recorded changes yet.

Sources

CVE.org / MITRE

Status PUBLISHED

Assigner mozilla

Published Jun 11, 2018

Updated Aug 5, 2024

Reserved Jan 3, 2018

Link CVE-2018-5174

CISA Vulnrichment

Updated n/a

NVD

Status Modified

Modified Jun 17, 2026

Link CVE-2018-5174

Red Hat

Severity Moderate

Public date May 9, 2018

Links CVE-2018-5174 - Bugzilla