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.
CVE-2018-5174
HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence
Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2022-05-13. NVD baseline CVSS 7.5; sources differ by 0.0.
Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 2%CVSS: 7.5Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(medium)
- EPSS
- 76.8%
- KEV
- Not listed
Published
June 11, 2018
Last Modified
November 25, 2025
References (12)
- security@mozillahttp://www.securityfocus.com/bid/104136
- security@mozillahttp://www.securitytracker.com/id/1040896
- security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=1447080
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2018-11/
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2018-12/
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2018-13/
- af854a3a-2127-422b-91ae-364da2661108http://www.securityfocus.com/bid/104136
- af854a3a-2127-422b-91ae-364da2661108http://www.securitytracker.com/id/1040896
- af854a3a-2127-422b-91ae-364da2661108https://bugzilla.mozilla.org/show_bug.cgi?id=1447080
- af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2018-11/
- af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2018-12/
- af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2018-13/
Data Freshness Timeline
(refreshed 12× in last 7d / 49× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
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- 2026-05-28 06:45 UTCEG score recompute
- 2026-05-28 06:45 UTCGHSA enrichment
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Frequently asked(5)
What is CVE-2018-5174?
CVE-2018-5174 is a high vulnerability published on June 11, 2018. In the Windows 10 April 2018 Update, Windows Defender SmartScreen honors the "SEEMASKFLAGNOUI" 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…
When was CVE-2018-5174 disclosed?
CVE-2018-5174 was first published in the National Vulnerability Database on June 11, 2018, with the most recent update on November 25, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2018-5174 actively exploited?
CVE-2018-5174 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 76.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2018-5174?
CVE-2018-5174 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2018-5174?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2018-5174, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
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