FirefoxWeb browser · Mozilla
CVE-2018-5118
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThe screenshot images displayed in the Activity Stream page displayed when a new tab is opened is created from the meta tags of websites. An issue was discovered where the page could attempt to create these images through "file:" URLs from the local file system. This loading is blocked by the sandbox but could expose local data if combined with another attack that escapes sandbox protections. This vulnerability affects Firefox < 58.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceFirefox's Activity Stream (new tab page) attempted to generate screenshot previews from website meta tags, including through 'file:' URLs pointing to the local file system. While the sandbox blocked direct access, this could expose local file contents if an attacker first exploited another vulnerability to escape the sandbox.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FirefoxWeb browser
<= 57.0.4
Ubuntu LinuxOperating system
= 14.04= 16.04= 17.10CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed Firefox versionOpen Firefox, go to Help > About Firefox, or run 'firefox --version' from command line, or check '/usr/lib/firefox/firefox --version'Affected if Version is 57.0.4 or lower
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Check Firefox package version on UbuntuRun 'dpkg -l | grep firefox' or 'apt-cache policy firefox' in terminalAffected if Package version is <= 57.0.4+build1-0ubuntu0.1 or similar 57.0.4 based packages for Ubuntu 14.04, 16.04, or 17.10
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Verify Activity Stream is in useOpen a new tab - the Activity Stream new tab page shows sponsored tiles and top sites. This feature is enabled by default in Firefox 57+. There is no user-facing toggle; checking the Firefox version alone determines exposure.Affected if Firefox version is 57.0.4 or lower (Activity Stream cannot be disabled as a detection step - the version check is sufficient)
You are affected if Firefox version is 57.0.4 or lower, as this version contains the vulnerable Activity Stream code that processes meta tags including file: URLs.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade to Firefox 58 or later. This is a vendor-patched vulnerability; no custom code changes are needed.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-5118 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-5118 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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