# CVE-2018-5174: Security feature bypass in Firefox

> Firefox incorrectly sets a flag that bypasses Windows SmartScreen prompts, allowing potentially dangerous files to run without user confirmation.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Jun 2018
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-cx2r-fxw7-w76f

## What is CVE-2018-5174?

CVE-2018-5174 is a high-severity vulnerability in Mozilla Firefox, published on 11 Jun 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

## Which versions are affected by CVE-2018-5174?

It affects 3 products.


Products: Mozilla Firefox, Mozilla Thunderbird, Mozilla Thunderbird Esr.

## How do I fix CVE-2018-5174?

Upgrade to a fixed version.

## Is CVE-2018-5174 being exploited?

There is no known exploitation of CVE-2018-5174 in the wild and no public exploit code.

## Other vulnerabilities in Mozilla Firefox

- [CVE-2019-11708](https://insights.sbomify.com/CVE-2019-11708/): Mozilla Firefox and Thunderbird Sandbox Escape (critical 10.0, exploited in the wild)
- [CVE-2010-3765](https://insights.sbomify.com/CVE-2010-3765/): Mozilla Multiple Products Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2022-26486](https://insights.sbomify.com/CVE-2022-26486/): Mozilla Firefox Use-After-Free (critical 9.6, exploited in the wild)
- [CVE-2022-26485](https://insights.sbomify.com/CVE-2022-26485/): Mozilla Firefox Use-After-Free (high 8.8, exploited in the wild)
- [CVE-2019-11707](https://insights.sbomify.com/CVE-2019-11707/): Mozilla Firefox and Thunderbird Type Confusion (high 8.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-5174 and fix it if it is affected.

What it is: CVE-2018-5174 is a high-severity vulnerability in Mozilla Firefox, published on 11 Jun 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-5174 in the wild and no public exploit code.

Affected product: Mozilla Firefox. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2018-5174/ (Markdown: https://insights.sbomify.com/CVE-2018-5174/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-5174
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-5174
- OSV: https://osv.dev/vulnerability/CVE-2018-5174

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-5174/
Summaries are generated and may contain mistakes; the official description above is the record.