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FirefoxWeb browser · Mozilla

CVE-2026-2769

HIGH · 8.8 CVSS v3.1 Published 2026-02-24
Fix available
A fix is available. Upgrade to 115.33.0 / 140.8.0 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
Use-after-free in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, 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

Use-after-free vulnerability in the Storage: IndexedDB component of Firefox and Thunderbird. This memory safety issue allows freed memory to be accessed, potentially leading to arbitrary code execution or crashes. The vulnerability has a CVSS score of 8.8 (HIGH), indicating significant risk.

MitigationUpgrade to Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, or Thunderbird 140.8 (or later versions) to remediate this vulnerability.

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:< 115.33.0< 148.0>= 128.0, < 140.8.0
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
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. Identify the installed Firefox version
    Open Firefox, go to Help > About Firefox (or navigate to about:support). The version number is displayed at the top.
    Affected if The version shown is less than 115.33.0, or is 128.0 or higher but less than 140.8.0, or is less than 148.0 (all of these ranges indicate vulnerability).
  2. Identify the installed Thunderbird version
    Open Thunderbird, go to Help > About Thunderbird. The version number is displayed.
    Affected if The version shown is less than 140.8.0 or less than 148.0.
  3. Verify IndexedDB is in use
    In Firefox, open the Web Developer Tools (F12), go to the Storage tab, and look for IndexedDB entries under the Storage section. Alternatively, visit a site known to use IndexedDB and check if data appears in about:storage.
    Affected if IndexedDB storage is present and accessible in the browser profile, indicating the vulnerable component is active.
  4. Check for browser updates
    In Firefox, go to Help > About Firefox. If an update is available, it will show a button to download and install it. In Thunderbird, check for updates via Help > Check for Updates.
    Affected if An update is available that would upgrade the version beyond the vulnerable ranges (115.33.0+, 140.8.0+, or 148.0+).

You are affected if you run Firefox version lower than 115.33.0, or 128.0-140.7.x, or lower than 148.0; or Thunderbird version lower than 140.8.0 or lower than 148.0, and IndexedDB storage is in use.

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 115.33.0 / 140.8.0 / 148.0 or later
Fixed in 115.33.0140.8.0148.0
Interim mitigation

Upgrade to Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, or Thunderbird 140.8 (or later versions) to remediate this vulnerability.

Recommended fix High confidence

Firefox 148.0 (or Firefox ESR 115.33.0 / Firefox ESR 140.8.0); Thunderbird 148.0 (or Thunderbird 140.8.0)

  1. 1. Open Firefox or Thunderbird and navigate to the Help menu.
  2. 2. Select 'About Firefox' or 'About Thunderbird' to check the current version.
  3. 3. If the version is below 148.0 for Firefox, or below 140.8.0 for Thunderbird (or below 115.33.0 for Firefox ESR 115.x), click 'Check for Updates' or allow automatic updates to complete.
  4. 4. Restart the application after the update installs.
  5. 5. Verify the version is now at 148.0 or higher (Firefox), 140.8.0 or higher (Thunderbird), or 115.33.0 or higher (Firefox ESR 115.x).

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2026-2769 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