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FirefoxWeb browser · Mozilla

CVE-2018-5138

MEDIUM · 5.3 CVSS v3.0 Published 2018-06-11
Fix available
A fix is available. Upgrade to 59.0 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
A spoofing vulnerability can occur when a malicious site with an extremely long domain name is opened in an Android Custom Tab (a browser panel inside another app) and the default browser is Firefox for Android. This could allow an attacker to spoof which page is actually loaded and in use. Note: this issue only affects Firefox for Android. Other versions and operating systems are unaffected. This vulnerability affects Firefox < 59.

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 confidence

A URL spoofing vulnerability in Firefox for Android (versions before 59) allows attackers to hide the true origin of a page when a site with an extremely long domain name is opened in an Android Custom Tab (an embedded browser panel). The long domain name obscures the actual URL, enabling spoofing of the displayed page.

MitigationUpgrade Firefox for Android to version 59 or later. Users should verify their default browser settings and ensure any apps using Custom Tabs are using an updated Firefox version.

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:< 59.0

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
None
Integrity
Low
Availability
None

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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. Verify Firefox for Android is installed
    Check device app list or use 'adb shell pm list packages' to see if org.mozilla.firefox is present
    Affected if Firefox for Android package exists on the device
  2. Check installed Firefox version
    Open Firefox for Android, tap Settings, scroll to Help, and tap About Firefox to view the version number
    Affected if The displayed version is below 59.0
  3. Identify Custom Tab usage
    Review installed apps for any that invoke Android Custom Tabs (embedded browser panels), or inspect app network behavior for Custom Tab sessions
    Affected if Any applications using Custom Tabs are present on the device

A user is affected if Firefox for Android version below 59.0 is installed AND apps using Android Custom Tabs are present on the device.

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 59.0 or later
Fixed in 59.0
Interim mitigation

Upgrade Firefox for Android to version 59 or later. Users should verify their default browser settings and ensure any apps using Custom Tabs are using an updated Firefox version.

Fix this in Firefox Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,440
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,304.

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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-2018-5138 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