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FirefoxWeb browser · Mozilla

CVE-2018-5128

CRITICAL · 9.8 CVSS v3.0 Published 2018-06-11
Fix available
A fix is available. Upgrade to 59.0 or later.
See remediation →
100/100
Remediation priority · Urgent
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 use-after-free vulnerability can occur when manipulating elements, events, and selection ranges during editor operations. This results in a potentially exploitable crash. 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 use-after-free vulnerability in Mozilla Firefox's editor component allows remote attackers to potentially execute arbitrary code by manipulating DOM elements, events, and selection ranges during editor operations, causing memory corruption after objects are freed.

MitigationUpgrade to Firefox version 59 or later to apply the security patch; if immediate patching is not feasible, restrict access to editor functionality until the upgrade can be performed.

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
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
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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 installed Firefox version
    Navigate to menu > Help > About Firefox, or enter 'about:support' in the address bar, or run 'firefox --version' from command line
    Affected if Version displayed is below 59.0 (for example 58.x, 57.x, or earlier)
  2. Check Ubuntu Firefox package version (if on Ubuntu)
    Run command: 'dpkg -l | grep firefox' or 'apt-cache policy firefox' in terminal
    Affected if Package version shown is earlier than 59.0+build1 or equivalent Firefox 59 release in Ubuntu repositories
  3. Verify editor component is accessible
    Check if user can access contenteditable web content, rich text input areas, or use Firefox's built-in editor features
    Affected if Editor functionality (contenteditable elements, rich text editing) is available and usable in the browser environment
  4. Check browser configuration for editor-related features
    Inspect 'about:config' for editor-related preferences such as 'editor.htmlbar.enabled' or examine whether the browser has addons that expose editor functionality
    Affected if Editor-related features or extensions are enabled that expose the vulnerable editor component

The environment is affected if Firefox version is below 59.0 (or Ubuntu Firefox package predates the fixed version) and the editor component is accessible to the user.

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.

dbcve · scoped
Upgrade available Upgrade to 59.0 or later
Fixed in 59.0
Interim mitigation

Upgrade to Firefox version 59 or later to apply the security patch; if immediate patching is not feasible, restrict access to editor functionality until the upgrade can be performed.

Recommended fix High confidence

Firefox 59.0

  1. Check current Firefox version by navigating to about:firefox or running 'firefox --version'
  2. Update Firefox to version 59.0 or later via the official Mozilla website or system package manager
  3. On Ubuntu Linux, run 'sudo apt-get update && sudo apt-get upgrade firefox' to apply security updates
  4. Restart Firefox after the update completes
  5. Verify the installed version is 59.0 or higher

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation0.5 h
  • Testing1.0 h
  • Review / QA0.5 h
3.0 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.

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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-2018-5128 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