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FirefoxWeb browser · Mozilla

CVE-2026-8389

HIGH · 8.8 CVSS v3.1 Published 2026-05-12
Fix available
A fix is available. Upgrade to 150.0.3 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

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
JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 150.0.3.

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 · low confidence

This is a JIT (Just-In-Time) miscompilation vulnerability in the Firefox JavaScript Engine's JIT component. The miscompilation can lead to memory corruption allowing potentially arbitrary code execution. Fixed in Firefox version 150.0.3.

MitigationUpdate Firefox to version 150.0.3 or later to apply the security patch.

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:< 150.0.3

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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
    Open Firefox, click the menu button (three lines), select Help, then select About Firefox. The version number will display on the page that opens.
    Affected if The version shown is less than 150.0.3 (for example, 150.0, 149.x, 148.x, or any earlier version)
  2. Verify JIT compiler status
    The JIT compiler is enabled by default in Firefox for JavaScript performance. To confirm it is active, type 'about:support' in the address bar, then search for 'JavaScript' in the page. Look for 'JIT Compiler' listed as enabled.
    Affected if JIT Compiler shows as enabled (this is the default state; the vulnerability applies when JIT is active)

If your Firefox version is below 150.0.3 and the JIT compiler is enabled (default), your environment is affected by this vulnerability.

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 150.0.3 or later
Fixed in 150.0.3
Interim mitigation

Update Firefox to version 150.0.3 or later to apply the security patch.

Recommended fix High confidence

Firefox 150.0.3

  1. Check current Firefox version by navigating to about:support or using the Help > About Firefox menu
  2. Download Firefox 150.0.3 or a later stable release from the official Mozilla website (www.mozilla.org)
  3. Close all Firefox instances
  4. Install the downloaded Firefox version
  5. Restart Firefox and verify the version is 150.0.3 or later
Caveat Minor browser updates may occasionally affect extension compatibility; test critical extensions after upgrade

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Testing1.0 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.

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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-2026-8389 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