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FirefoxWeb browser · Mozilla

CVE-2020-6814

CRITICAL · 9.8 CVSS v3.1 Published 2020-03-25
Fix available
A fix is available. Upgrade to 68.6.0 / 74.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 and Thunderbird 68.5. 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 Thunderbird < 68.6, Firefox < 74, Firefox < ESR68.6, and Firefox ESR < 68.6.

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 confidence

Memory safety bugs in Firefox and Thunderbird 68.5 led to memory corruption vulnerabilities that could potentially be exploited for arbitrary code execution. This is a critical client-side vulnerability affecting multiple Mozilla products.

MitigationUpgrade affected installations to Thunderbird 68.6+, Firefox 74+, or Firefox ESR 68.6+ to receive the patched versions containing the memory safety fixes.

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:< 74.0
Firefox EsrWeb browser
Affected:< 68.6.0
Ubuntu LinuxOperating system
Affected:= 16.04= 18.04= 19.10
ThunderbirdApplication
Affected:< 68.6.0

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
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 checks

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

  1. Check installed Firefox version
    Run 'firefox --version' or 'firefox -v' in terminal, or navigate to Firefox menu > Help > About Firefox
    Affected if Version is below 74.0 (for example, 73.x or earlier)
  2. Check installed Firefox ESR version
    Run 'firefox --version' and verify ESR status via 'firefox -v' output which typically shows 'Mozilla Firefox ESR' in the version string
    Affected if Version is below 68.6.0 and is the ESR release
  3. Check installed Thunderbird version
    Run 'thunderbird --version' or 'thunderbird -v' in terminal, or navigate to Thunderbird menu > Help > About Thunderbird
    Affected if Version is below 68.6.0
  4. Check Ubuntu system Mozilla package versions
    Run 'dpkg -l | grep -i firefox' or 'apt list --installed | grep -i firefox' on Ubuntu systems to list installed Mozilla package versions
    Affected if Ubuntu 16.04, 18.04, or 19.10 has Firefox packages installed (these releases shipped with vulnerable Firefox versions)

A user is affected if Firefox (including ESR) is below version 74.0, Thunderbird is below 68.6.0, or the system runs Ubuntu 16.04/18.04/19.10 with bundled Firefox packages.

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 68.6.0 / 74.0 or later
Fixed in 68.6.074.0
Interim mitigation

Upgrade affected installations to Thunderbird 68.6+, Firefox 74+, or Firefox ESR 68.6+ to receive the patched versions containing the memory safety fixes.

Recommended fix High confidence

Firefox 74.0+, Firefox ESR 68.6.0+, Thunderbird 68.6.0+

  1. Back up any critical data (bookmarks, emails, passwords) before upgrading
  2. Update Firefox to version 74.0 or later: On Windows/macOS, use Help > About Firefox > Check for Updates, or download from https://www.mozilla.org/firefox/
  3. Update Thunderbird to version 68.6.0 or later: Use Help > About Thunderbird > Check for Updates, or download from https://www.thunderbird.net/
  4. For Ubuntu Linux systems, run: sudo apt update && sudo apt upgrade (or sudo apt full-upgrade) to receive security updates for Firefox/Thunderbird from Ubuntu repositories
  5. For Ubuntu 16.04 (EOL), enable ESM (Extended Security Maintenance) if still receiving updates, or upgrade to a newer Ubuntu LTS version
  6. Verify the updated version by checking: Firefox: Navigate to about:support, Thunderbird: Help > About Thunderbird
Caveat Minimal risk for browser/email client upgrades; major version jumps (e.g., Firefox 68 to 74) may occasionally affect legacy extensions or add-ons

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
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

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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-2020-6814 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