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FirefoxWeb browser · Mozilla

CVE-2026-2803

HIGH · 7.5 CVSS v3.1 Published 2026-02-24
Fix available
A fix is available. Upgrade to 148.0 or later.
See remediation →
84/100
Remediation priority · High
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
Information disclosure, mitigation bypass in the Settings UI component. This vulnerability was fixed in Firefox 148 and Thunderbird 148.

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 · moderate confidence

This is an information disclosure vulnerability with a mitigation bypass affecting the Settings UI component in Firefox and Thunderbird. The vulnerability allows bypassing existing security controls to expose sensitive information through the Settings interface. The issue was addressed in Firefox 148 and Thunderbird 148.

MitigationUpdate to Firefox 148 or Thunderbird 148 or later to obtain the security fix.

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:< 148.0
ThunderbirdApplication
Affected:< 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
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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 by looking for their executable paths (Firefox: typically in Program Files/Mozilla Firefox or /Applications/Firefox.app; Thunderbird: typically in Program Files/Mozilla Thunderbird or /Applications/Thunderbird.app). On Linux, check for 'firefox' or 'thunderbird' commands using 'which firefox' or 'which thunderbird'.
    Affected if Either Firefox or Thunderbird is present on the system
  2. Check Firefox version
    For Firefox: Go to menu > Help > About Firefox, or type 'about:support' in the address bar, or run 'firefox --version' from command line. Note the full version number (e.g., 147.0, 147.0.1, etc.).
    Affected if Firefox version is below 148.0 (e.g., 147.x, 146.x, etc.)
  3. Check Thunderbird version
    For Thunderbird: Go to menu > Help > About Thunderbird, or type 'about:support' in the address bar, or run 'thunderbird --version' from command line. Note the full version number.
    Affected if Thunderbird version is below 148.0 (e.g., 147.x, 146.x, etc.)

If either Firefox or Thunderbird is installed with a version lower than 148.0, the environment is affected by this information disclosure vulnerability in the Settings UI.

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 148.0 or later
Fixed in 148.0
Interim mitigation

Update to Firefox 148 or Thunderbird 148 or later to obtain the security fix.

Recommended fix High confidence

Firefox 148.0 and Thunderbird 148.0 (or later)

  1. For Firefox: Open Firefox, navigate to Menu > Help > About Firefox to check current version and trigger automatic update to 148.0 or later
  2. For Firefox: Alternatively, download Firefox 148.0 or later from the official Mozilla website (www.mozilla.org) and install over the existing version
  3. For Thunderbird: Open Thunderbird, navigate to Menu > Help > About Thunderbird to check current version and trigger automatic update to 148.0 or later
  4. For Thunderbird: Alternatively, download Thunderbird 148.0 or later from the official Mozilla website (www.mozilla.org) and install over the existing version
  5. After updating, verify the version number matches 148.0 or higher in the About dialog

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 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-2026-2803 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