FirefoxWeb browser · Mozilla
CVE-2026-8390
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 · uneditedUse-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 150.0.3.
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 · high confidenceA use-after-free vulnerability exists in Firefox's JavaScript WebAssembly component. This memory corruption issue allows freed memory to be accessed, potentially leading to arbitrary code execution or browser crashes. The vulnerability was addressed in Firefox version 150.0.3.
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
< 150.0.3CVSS 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
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
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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Check installed Firefox versionOpen Firefox, click the menu button (three lines), select Help, then About Firefox. The version number will display in the window that opens.Affected if The displayed version is below 150.0.3 (for example, 150.0.2, 150.0.1, 150.0, 149.x, or earlier)
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Verify exact version numberIn the About Firefox window, confirm the full version string including any build numbers or release notes shown.Affected if The full version string is anything less than 150.0.3
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Confirm WebAssembly usage in browserVisit any website that uses WebAssembly (many modern web apps do). This vulnerability exists in Firefox's JavaScript WebAssembly component regardless of whether a specific site is actively using it.Affected if Firefox is used for web browsing and the version is below 150.0.3 - the component is present in all standard Firefox installations
You are affected if your installed Firefox version is anything below 150.0.3, since the vulnerable WebAssembly component is included in all standard Firefox installations.
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 · scoped150.0.3
Update Firefox to version 150.0.3 or later to remediate this vulnerability.
Firefox 150.0.3
- 1. Back up any important data and bookmarks in your current Firefox profile
- 2. Open Firefox and navigate to the Help menu (three horizontal lines in the top-right corner)
- 3. Select 'About Firefox' to check your current version
- 4. Click 'Update to [version]' when the update prompt appears, or Firefox will automatically download the update
- 5. Wait for the download to complete and restart Firefox when prompted
- 6. Verify the update by navigating to Help > About Firefox and confirm version 150.0.3 is installed
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 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-2026-8390 — 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-2026-8390 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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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.
- 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