dbcve.org
FirefoxWeb browser · Mozilla

CVE-2018-5092

CRITICAL · 9.8 CVSS v3.0 Published 2018-06-11
Fix available
A fix is available. Upgrade to after 57.0.4 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 the thread for a Web Worker is freed from memory prematurely instead of from memory in the main thread while cancelling fetch operations. 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 confidence

A use-after-free vulnerability in Firefox's Web Worker implementation allows premature memory deallocation of a worker thread during fetch operation cancellation. The thread is freed from memory incorrectly instead of being freed from the main thread, leading to potential memory corruption and arbitrary code execution.

MitigationUpgrade Firefox to version 58 or later to obtain the patch from Mozilla. Prioritize updates for systems running Firefox < 58, especially those handling sensitive operations or accessible to untrusted web content.

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
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
    Run 'firefox --version' in terminal, or navigate to 'about:Firefox' in the browser address bar, or check your system's package manager (dpkg -l firefox | grep firefox on Debian/Ubuntu, rpm -qi firefox on RHEL/Fedora)
    Affected if The version displayed is 57.0.4 or any earlier version (e.g., 57.0.3, 57.0.2, 56.x, etc.)
  2. Check Ubuntu OS version
    Run 'lsb_release -a' or 'cat /etc/lsb-release' in terminal
    Affected if The system reports Ubuntu 14.04, 16.04, or 17.10 AND Firefox version is at or below 57.0.4
  3. Check Firefox package installation source
    On Ubuntu/Debian: run 'dpkg -l | grep firefox' to see if Firefox was installed from the Mozilla Team PPA or standard repositories. On RHEL/Fedora: run 'rpm -qa | grep firefox'
    Affected if Firefox was installed via system package manager at a version <= 57.0.4 and has not been updated
  4. Verify Firefox update status
    In Firefox, navigate to 'about:support' and check 'Update Folder' and 'Updates' section, or check if Help > Check for Updates shows the browser is outdated
    Affected if The browser reports it is unable to update or shows no pending updates while the version is <= 57.0.4

You are affected if Firefox version is 57.0.4 or earlier, regardless of operating system, with heightened exposure on Ubuntu 14.04, 16.04, or 17.10 systems.

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 a release after 57.0.4
Interim mitigation

Upgrade Firefox to version 58 or later to obtain the patch from Mozilla. Prioritize updates for systems running Firefox < 58, especially those handling sensitive operations or accessible to untrusted web content.

Recommended fix High confidence

Firefox 58 or later

  1. Upgrade Firefox to version 58 or later to address the use-after-free vulnerability in Web Worker thread handling
  2. On Ubuntu/Linux systems, run: sudo apt-get update && sudo apt-get upgrade firefox
  3. Alternatively, download and install Firefox 58+ from the official Mozilla website: https://www.mozilla.org/
  4. Verify the installed version by navigating to about:Firefox in the address bar
Caveat Firefox 58+ may have compatibility changes for extensions; Firefox 57 introduced WebExtensions which replaced legacy add-ons

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Review / QA1.0 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.

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-2018-5092 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