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FirefoxWeb browser · Mozilla

CVE-2018-5119

MEDIUM · 5.3 CVSS v3.0 Published 2018-06-11
Fix available
A fix is available. Upgrade to after 57.0.4 or later.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

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 · unedited
The reader view will display cross-origin content when CORS headers are set to prohibit the loading of cross-origin content by a site. This could allow access to content that should be restricted in reader view. 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 · moderate confidence

Firefox's reader view fails to enforce CORS (Cross-Origin Resource Sharing) headers, allowing cross-origin content to be displayed even when the origin server explicitly prohibits such access. This is an access control bypass where content that should be restricted based on CORS policies is incorrectly rendered in reader view.

MitigationUpgrade Firefox to version 58 or later to receive the patch that properly enforces CORS restrictions in reader view.

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
Affected:<= 57.0.4
Ubuntu LinuxOperating system
Affected:= 14.04= 16.04= 17.10

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Check Firefox browser version
    Open Firefox, navigate to Help > About Firefox, or type 'about:support' in the address bar to view the version number under Application Basics > Version
    Affected if The displayed version number is 57.0.4 or lower (any version up to and including 57.0.4)
  2. Check Firefox version via command line (Linux)
    Run 'firefox --version' or 'apt list --installed | grep firefox' in a terminal to retrieve the installed Firefox package version
    Affected if The reported version is 57.0.4 or lower, or the package version string contains a version number up to 57.0.4
  3. Check Ubuntu system package version
    On Ubuntu systems, run 'dpkg -l | grep firefox' or check the package details via 'apt-cache policy firefox' to see the installed version
    Affected if The installed firefox package version corresponds to 57.0.4 or earlier for the affected Ubuntu releases (14.04, 16.04, 17.10)

A user is affected if their installed Firefox browser version is 57.0.4 or lower, regardless of operating system, because reader view in those versions bypasses CORS restrictions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to a release after 57.0.4
Interim mitigation

Upgrade Firefox to version 58 or later to receive the patch that properly enforces CORS restrictions in reader view.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2018-5119 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data