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FirefoxWeb browser · Mozilla

CVE-2026-2768

CRITICAL · 10.0 CVSS v3.1 Published 2026-02-24
Fix available
A fix is available. Upgrade to 140.8.0 / 148.0 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
Sandbox escape in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

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

This is a sandbox escape vulnerability in the IndexedDB storage component of Firefox and Thunderbird. A sandbox escape allows an attacker to break out of the security sandbox that isolates web content, potentially gaining elevated privileges or access to the underlying system. The vulnerability was addressed in the specified Firefox and Thunderbird versions.

MitigationUpgrade to Firefox 148 (or ESR 140.8), Thunderbird 148 (or 140.8), or later versions to apply the security fix. For enterprise environments, deploy the updated versions via software management or patch management systems.

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:< 140.8.0< 148.0
ThunderbirdApplication
Affected:< 140.8.0< 148.0

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
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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. Identify installed Mozilla product
    Check if Firefox or Thunderbird is installed. In Windows, look in Program Files or Program Files (x86). On macOS, check /Applications. On Linux, check /usr/lib/firefox or /usr/lib/thunderbird.
    Affected if Any version of Firefox or Thunderbird is installed
  2. Check Firefox version
    In Firefox, navigate to Menu > Help > About Firefox, or enter 'about:support' in the address bar. The version number is displayed on the page that opens.
    Affected if Version is below 140.8.0 or between 140.8.0 and 147.x (any version below 148.0)
  3. Check Thunderbird version
    In Thunderbird, navigate to Menu > Help > About Thunderbird. The version number is displayed on the page that opens.
    Affected if Version is below 140.8.0 or between 140.8.0 and 147.x (any version below 148.0)
  4. Check Firefox ESR version
    Firefox ESR versions are typically installed in enterprise environments. Check via Menu > Help > About Firefox. ESR versions include 'ESR' in the version string, such as '140.8esr'.
    Affected if ESR version is below 140.8.0

The environment is affected if Firefox, Firefox ESR, or Thunderbird is installed with any version below 148.0 (or below 140.8.0 for ESR branch).

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 140.8.0 / 148.0 or later
Fixed in 140.8.0148.0
Interim mitigation

Upgrade to Firefox 148 (or ESR 140.8), Thunderbird 148 (or 140.8), or later versions to apply the security fix. For enterprise environments, deploy the updated versions via software management or patch management systems.

Recommended fix High confidence

Firefox 148.0 (standard) or Firefox ESR 140.8.0; Thunderbird 148.0 (standard) or Thunderbird ESR 140.8.0

  1. Open Firefox/Thunderbird and navigate to Help > About [Application Name] to check current version
  2. If version is below 140.8.0, install Firefox ESR 140.8.0 or later from mozilla.org
  3. If version is below 148.0 (and not on ESR), install Firefox 148.0 or later from mozilla.org
  4. For Thunderbird users: Apply the same version logic (Thunderbird 140.8.0 for ESR, Thunderbird 148.0 for standard)
  5. Restart the application after upgrade
  6. Verify the new version in Help > About to confirm installation
Caveat Some legacy add-ons may be incompatible with major version upgrades; verify extension compatibility before upgrading in enterprise environments

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $910
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,456.

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-2026-2768 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