FirefoxWeb browser · Mozilla
CVE-2026-2798
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 DOM: Core & HTML component. This vulnerability was fixed in Firefox 148 and Thunderbird 148.
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 confidenceUse-after-free vulnerability in the DOM Core & HTML component of Firefox and Thunderbird. This memory safety flaw allows freed memory to be accessed, potentially leading to arbitrary code execution or renderer process crashes.
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
< 148.0< 148.0CVSS 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
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 checksWork through these to decide whether this CVE applies to you.
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Check if Mozilla Firefox is installedOpen Firefox and navigate to Help > About Firefox, or type 'about:support' in the address bar to view the version numberAffected if Firefox version is less than 148.0
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Check if Mozilla Thunderbird is installedOpen Thunderbird and navigate to Help > About Thunderbird, or check the application version through your system's installed programs listAffected if Thunderbird version is less than 148.0
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Verify the exact version numberNote the full version string displayed in the About dialog (for example, 147.1 or 147.0.1)Affected if The installed version number is below 148.0 (any 147.x, 146.x, or earlier version)
You are affected if either Mozilla Firefox or Thunderbird is installed with a version number lower than 148.0, since this UAF vulnerability exists in the DOM: Core & HTML component of those earlier versions.
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 · scoped148.0
Deploy Firefox 148 and Thunderbird 148 or later to all affected systems to eliminate the vulnerability.
Firefox 148.0 and Thunderbird 148.0
- 1. Back up any important data such as bookmarks, passwords, and email data in Thunderbird
- 2. Open Firefox or Thunderbird
- 3. Navigate to the application menu (three horizontal lines) and select 'Help' > 'About Firefox' or 'About Thunderbird'
- 4. The application will check for updates automatically and display the current version
- 5. If the version is below 148.0, download and install Firefox 148.0 or Thunderbird 148.0 from the official Mozilla website (www.mozilla.org)
- 6. Restart the application after installation
- 7. Verify the version by returning to 'About' to confirm version 148.0 or later is installed
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
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
Free · runs locallyCheck whether your project pulls in CVE-2026-2798 — 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-2026-2798 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