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FirefoxWeb browser · Mozilla

CVE-2025-9185

HIGH · 8.1 CVSS v3.1 Published 2025-08-19
Fix available
A fix is available. Upgrade to 115.27.0 / 128.14.0 or later.
See remediation →
90/100
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
Memory safety bugs present in Firefox ESR 115.26, Firefox ESR 128.13, Thunderbird ESR 128.13, Firefox ESR 140.1, Thunderbird ESR 140.1, Firefox 141 and Thunderbird 141. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 142, Firefox ESR 115.27, Firefox ESR 128.14, Firefox ESR 140.2, Thunderbird 142, Thunderbird 128.14, and Thunderbird 140.2.

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

Multiple memory safety bugs in Firefox and Thunderbird allowed memory corruption that could potentially be exploited for arbitrary code execution. The issues affected multiple ESR branches (115.x, 128.x, 140.x) and stable versions 141.

MitigationUpdate all affected Firefox and Thunderbird installations to the patched versions (Firefox 142, Firefox ESR 115.27/128.14/140.2, Thunderbird 142, Thunderbird 128.14/140.2). This is a client-side vulnerability requiring user action or enterprise patch deployment.

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:< 115.27.0< 142.0>= 128.0, < 128.14.0>= 140.0, < 140.2.0
ThunderbirdApplication
Affected:< 128.14.0< 142.0>= 140.0, < 140.2.0

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/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. Detect installed Firefox version
    Run 'firefox --version' or check Help > About Firefox in the application menu. On Windows, open Firefox and go to Help > About Firefox. On macOS, run 'firefox --version' in Terminal or click Firefox > About Firefox.
    Affected if Version is < 115.27.0, OR between 128.0.0 and 128.13.0 inclusive, OR between 140.0.0 and 140.1.0 inclusive, OR < 142.0 (for versions 141.x)
  2. Detect installed Thunderbird version
    Run 'thunderbird --version' or check Help > About Thunderbird in the application menu. On Windows, open Thunderbird and go to Help > About Thunderbird. On macOS, run 'thunderbird --version' in Terminal or click Thunderbird > About Thunderbird.
    Affected if Version is < 128.14.0, OR between 140.0.0 and 140.1.0 inclusive, OR < 142.0 (for version 141.x)
  3. Identify all Firefox installations in the environment
    On Linux, check /usr/bin/firefox and ~/.mozilla. On Windows, check C:\Program Files\Mozilla Firefox and C:\Program Files (x86)\Mozilla Firefox. On macOS, check /Applications/Firefox.app. List all found versions using the --version flag for each binary.
    Affected if Any Firefox installation matches the version ranges in step 1

You are affected if any installed Firefox version is < 115.27.0, 128.0.x through 128.13.x, 140.0.x through 140.1.x, or 141.x; OR any installed Thunderbird version is < 128.14.0, 140.0.x through 140.1.x, or 141.x.

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 115.27.0 / 128.14.0 / 140.2.0 or later
Fixed in 115.27.0128.14.0140.2.0
Interim mitigation

Update all affected Firefox and Thunderbird installations to the patched versions (Firefox 142, Firefox ESR 115.27/128.14/140.2, Thunderbird 142, Thunderbird 128.14/140.2). This is a client-side vulnerability requiring user action or enterprise patch deployment.

Recommended fix High confidence

Firefox 142, Firefox ESR 115.27/128.14/140.2, Thunderbird 142, or Thunderbird ESR 128.14/140.2 (depending on which release channel you are on)

  1. Identify the currently installed Firefox or Thunderbird version via Help > About (or running: firefox --version or thunderbird --version)
  2. For Firefox users on versions 115.x: upgrade to Firefox ESR 115.27 or later
  3. For Firefox users on versions 128.x: upgrade to Firefox ESR 128.14 or later
  4. For Firefox users on versions 140.x-141.x: upgrade to Firefox ESR 140.2 or Firefox 142
  5. For Thunderbird users on versions 128.x: upgrade to Thunderbird ESR 128.14 or later
  6. For Thunderbird users on versions 140.x-141.x: upgrade to Thunderbird ESR 140.2 or Thunderbird 142
  7. After upgrade, verify the new version via Help > About to confirm the fix is applied
Caveat Standard version upgrade; review release notes for any add-on compatibility changes in major version jumps

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
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

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-2025-9185 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