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FirefoxWeb browser · Mozilla

CVE-2025-10533

HIGH · 8.8 CVSS v3.1 Published 2025-09-16
Fix available
A fix is available. Upgrade to 115.28.0 / 140.3 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable 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
Integer overflow in the SVG component. This vulnerability was fixed in Firefox 143, Firefox ESR 115.28, 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

An integer overflow vulnerability exists in the SVG (Scalable Vector Graphics) component of Mozilla Firefox and Thunderbird. This type of flaw occurs when an arithmetic operation produces a value larger than the allocated memory can hold, potentially leading to heap-based buffer overflows, out-of-bounds memory writes, or memory corruption during SVG rendering.

MitigationUpdate affected systems to Firefox 143, Firefox ESR 115.28, Firefox ESR 140.3, Thunderbird 143, Thunderbird 140.3 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:< 115.28.0< 143.0>= 116.0, < 140.3
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
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/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 if Mozilla Firefox is installed
    Check for Firefox installation by looking for the executable. On Windows: check for 'C:\Program Files\Mozilla Firefox\firefox.exe'. On Linux: run 'which firefox' or check '/usr/bin/firefox'. On macOS: check '/Applications/Firefox.app'.
    Affected if Firefox is installed and the version falls below 115.28.0, or is between 116.0 and 140.3, or is below 143.0
  2. Get the installed Firefox version number
    Open Firefox and navigate to 'about:firefox' in the address bar, or from the menu go to Help > About Firefox. Alternatively, run 'firefox --version' from command line on Linux.
    Affected if The displayed version number is less than 115.28.0, or falls between 116.0 and 140.3, or is less than 143.0
  3. Identify if Mozilla Thunderbird is installed
    Check for Thunderbird installation. On Windows: check for 'C:\Program Files\Mozilla Thunderbird\thunderbird.exe'. On Linux: run 'which thunderbird' or check '/usr/bin/thunderbird'. On macOS: check '/Applications/Thunderbird.app'.
    Affected if Thunderbird is installed and the version falls below 140.3.0, or is between 141.0 and 143.0
  4. Get the installed Thunderbird version number
    Open Thunderbird and navigate to 'about:thunderbird' in the address bar, or from the menu go to Help > About Thunderbird. Alternatively, run 'thunderbird --version' from command line on Linux.
    Affected if The displayed version number is less than 140.3.0, or falls between 141.0 and 143.0

Your environment is affected if either Mozilla Firefox version is below 115.28.0, between 116.0-140.3, or below 143.0, OR if Mozilla Thunderbird version is below 140.3.0 or between 141.0-143.0, and the SVG rendering feature 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 115.28.0 / 140.3 / 140.3.0 or later
Fixed in 115.28.0140.3140.3.0
Interim mitigation

Update affected systems to Firefox 143, Firefox ESR 115.28, Firefox ESR 140.3, Thunderbird 143, Thunderbird 140.3 or later versions to remediate this vulnerability.

Recommended fix High confidence

Firefox 143.0, Firefox ESR 115.28.0, Firefox ESR 140.3, Thunderbird 140.3, Thunderbird 143

  1. For Firefox: Navigate to Menu > Help > About Firefox to check current version
  2. Download and install Firefox 143.0 or later from mozilla.org
  3. For Firefox ESR: Download and install Firefox ESR 115.28.0 or later, or Firefox ESR 140.3 or later from mozilla.org
  4. For Thunderbird: Navigate to Menu > Help > About Thunderbird to check current version
  5. Download and install Thunderbird 140.3 or later, or Thunderbird 143 or later from mozilla.org
  6. Restart the application after upgrade
Caveat Standard version upgrades typically do not introduce breaking changes; always review release notes for notable changes

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

Fix this in Firefox Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,544.

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-2025-10533 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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