FirefoxWeb browser · Mozilla
CVE-2026-2797
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: GC 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 · high confidenceA use-after-free vulnerability exists in the JavaScript garbage collection (GC) component of Firefox and Thunderbird. This memory safety flaw allows an attacker to potentially execute arbitrary code or cause denial of service by accessing freed memory. The vulnerability was addressed in Firefox 148 and Thunderbird 148.
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
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/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 checksWork through these to decide whether this CVE applies to you.
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Check if Firefox is installed and get its versionOpen Firefox, go to Help > About Firefox, or run 'firefox --version' in terminal. On Windows, check Add/Remove Programs or the executable properties. On Linux, check your package manager: dpkg -l | grep firefox or rpm -qa | grep firefox.Affected if Firefox version is less than 148.0
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Check if Thunderbird is installed and get its versionOpen Thunderbird, go to Help > About Thunderbird, or run 'thunderbird --version' in terminal. On Windows, check Add/Remove Programs. On Linux, check your package manager: dpkg -l | grep thunderbird or rpm -qa | grep thunderbird.Affected if Thunderbird version is less than 148.0
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Compare installed versions against affected rangeReview the version numbers obtained from the previous checks. The affected version range is any version prior to 148.0 (for example, 147.x, 147.0.1, 146.x, etc.).Affected if Either Firefox or Thunderbird is installed with a version number lower than 148.0
You are affected if either Mozilla Firefox or Thunderbird is installed with a version lower than 148.0, as this is a core JavaScript GC component flaw present in all 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
Update Firefox and Thunderbird to version 148 or later through the application's built-in update mechanism or by downloading the latest version from the official Mozilla website.
Firefox 148.0 / Thunderbird 148.0
- 1. Back up any important data and bookmarks
- 2. Open Firefox or Thunderbird
- 3. Navigate to Help > About Firefox (or About Thunderbird)
- 4. Click 'Check for Updates' or allow the automatic check to complete
- 5. If version 148.0 or later is available, download and install it
- 6. Restart the application after the update completes
- 7. Alternatively, download Firefox 148.0 or Thunderbird 148.0 directly from the official Mozilla website (www.mozilla.org) and install over the current version
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-2026-2797 — 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-2026-2797 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