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FirefoxWeb browser · Mozilla

CVE-2021-38494

HIGH · 8.8 CVSS v3.1 Published 2021-11-03
Fix available
A fix is available. Upgrade to 92.0 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

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
Mozilla developers reported memory safety bugs present in Firefox 91. 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 affects Firefox < 92.

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 confidence

Memory safety bugs in Firefox 91 that could allow arbitrary code execution via memory corruption. Specific vulnerability details are not provided but the issues are present in the browser's memory handling.

MitigationUpdate Firefox to version 92 or later to patch the memory safety vulnerabilities.

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:< 92.0

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
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 checks

Work through these to decide whether this CVE applies to you.

  1. Check Firefox browser version
    Open Firefox, click the menu button (three horizontal lines), select Help, then select About Firefox. The version number will be displayed on this page.
    Affected if The displayed version number is less than 92.0 (for example, 91.x or earlier)
  2. Check Firefox version from command line
    Open a terminal or command prompt and run: firefox --version
    Affected if The output shows a version number less than 92.0 (for example, 91.0, 90.x, etc.)
  3. Verify Firefox installation path and version file
    Locate the Firefox executable in the installation directory and check its properties or metadata for the version. On Windows, this is typically in Program Files/Mozilla Firefox. On macOS, check /Applications/Firefox.app. On Linux, check /usr/lib/firefox or the distribution's package information.
    Affected if The version associated with the installed executable is less than 92.0

If Firefox version is below 92.0, the browser is affected by these memory safety vulnerabilities that could allow arbitrary code execution.

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 92.0 or later
Fixed in 92.0
Interim mitigation

Update Firefox to version 92 or later to patch the memory safety vulnerabilities.

Recommended fix High confidence

Firefox 92.0 or later

  1. Check current Firefox version by clicking Help > About Firefox
  2. Download Firefox 92 or later from the official Mozilla website (www.mozilla.org)
  3. Install the Firefox update

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

Scan for this in your stack

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dbcve dependency scanner

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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-2021-38494 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