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FirefoxWeb browser · Mozilla

CVE-2025-10536

MEDIUM · 6.2 CVSS v3.1 Published 2025-09-16
Fix available
A fix is available. Upgrade to 140.3.0 / 143.0 or later.
See remediation →
67/100
Remediation priority · Elevated
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 in the Networking: Cache component. This vulnerability was fixed in Firefox 143, Firefox ESR 140.3, Thunderbird 143, and Thunderbird 140.3.

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 · moderate confidence

Information disclosure vulnerability in the Networking: Cache component of Firefox and Thunderbird. The cache mechanism was improperly exposing sensitive data that should not have been accessible, potentially leaking cached credentials, session tokens, or other sensitive information to unauthorized contexts.

MitigationUpdate affected systems to Firefox 143, Firefox ESR 140.3, Thunderbird 143, or Thunderbird 140.3 or later to remediate the 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:< 140.3.0< 143.0
ThunderbirdApplication
Affected:< 140.3.0>= 141.0, < 143.0

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
Local
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:L/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. Check Firefox version
    Navigate to 'about:firefox' in the address bar or go to Help > About Firefox. Note the version number displayed.
    Affected if The version is earlier than 140.3.0 OR falls between 140.3.0 and 143.0 (exclusive of 143.0)
  2. Check Thunderbird version
    Go to Help > About Thunderbird. Note the version number displayed in the dialog.
    Affected if The version is earlier than 140.3.0 OR falls between 141.0 and 143.0 (exclusive of 143.0)
  3. Verify cache is in use (context check)
    The vulnerability affects the Networking: Cache component. To confirm the cache is active, check for cached content in your profile directory (typically in the 'cache2' folder within your profile folder). On Firefox, enter 'about:cache' in the address bar to view cache entries.
    Affected if Cache entries exist and your browser/client version falls within the affected ranges - this confirms exposure to the vulnerability

You are affected if you run Firefox or Thunderbird versions below 143.0 (with the specific exclusions noted in the version ranges) and the browser/client has been used to access sites that would cache sensitive data.

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 140.3.0 / 143.0 or later
Fixed in 140.3.0143.0
Interim mitigation

Update affected systems to Firefox 143, Firefox ESR 140.3, Thunderbird 143, or Thunderbird 140.3 or later to remediate the vulnerability.

Recommended fix High confidence

Firefox 143.0+, Firefox ESR 140.3.0+, Thunderbird 143.0+, or Thunderbird 140.3.0+

  1. Identify your current Firefox or Thunderbird version from the application menu (Help > About)
  2. For Firefox: Download and install Firefox 143.0 or later from www.mozilla.org/firefox
  3. For Firefox ESR users: Download and install Firefox ESR 140.3.0 or later from www.mozilla.org/firefox/organizations
  4. For Thunderbird: Download and install Thunderbird 143.0 or later from www.mozilla.org/thunderbird
  5. For Thunderbird ESR users: Download and install Thunderbird 140.3.0 or later from www.mozilla.org/thunderbird/organizations
  6. Restart the application after upgrade and verify the version in Help > About

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing1.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,270
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,032.

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-2025-10536 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