FirefoxWeb browser · Mozilla
CVE-2025-8036
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 · uneditedThunderbird cached CORS preflight responses across IP address changes. This allowed circumventing CORS with DNS rebinding. This vulnerability was fixed in Firefox 141, Firefox ESR 140.1, Thunderbird 141, and Thunderbird 140.1.
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 confidenceThunderbird cached CORS preflight responses in a way that persisted across IP address changes, allowing DNS rebinding attacks to bypass Cross-Origin Resource Sharing (CORS) protections and access resources from different origins.
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
< 140.1.0< 141.0< 140.1.0< 141.0CVSS 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
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify Thunderbird versionIn Thunderbird, go to Help > About Thunderbird to see the installed version numberAffected if Version is below 140.1.0 or below 141.0 (for example, 140.0 or earlier)
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Identify Firefox version if usedIn Firefox, go to Help > About Firefox to see the installed version numberAffected if Firefox is installed and version is below 140.1.0 or below 141.0
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Confirm CORS preflight caching behaviorThis vulnerability is in the CORS preflight response cache mechanism. The flaw allows cached preflight responses to remain valid after IP address changes, enabling DNS rebinding attacks. No special configuration check needed as this is a default browser behavior.Affected if Affected version is running and the browser makes CORS requests to external domains
You are affected if Thunderbird or Firefox version is below 140.1.0 or below 141.0, as these versions contain the vulnerable CORS preflight response caching that persists across IP address changes.
Generated from the published advisory. Verify against your own configuration.
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 · scoped140.1.0141.0
Update Thunderbird to version 140.1 or 141 (or later) to receive the fix for the CORS preflight caching vulnerability.
Firefox 141 (or ESR 140.1) / Thunderbird 141 (or ESR 140.1)
- Check current Firefox or Thunderbird version by navigating to Menu > Help > About (or running: firefox --version or thunderbird --version)
- For Firefox: Download and install Firefox 141 or later from the official Mozilla website (www.mozilla.org)
- For Thunderbird: Download and install Thunderbird 141 or later from the official Mozilla website (www.mozilla.org)
- For Firefox ESR: Download and install Firefox ESR 140.1 or later
- For Thunderbird ESR: Download and install Thunderbird 140.1 or later
- Restart the application after upgrade
- Verify the installed version matches or exceeds the fixed release (140.1.0 or 141.0)
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
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
Free · runs locallyCheck whether your project pulls in CVE-2025-8036 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-8036 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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