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FirefoxWeb browser · Mozilla

CVE-2026-6752

HIGH · 7.3 CVSS v3.1 Published 2026-04-21
Fix available
A fix is available. Upgrade to 115.35.0 / 140.10.0 or later.
See remediation →
82/100
Remediation priority · High
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
Incorrect boundary conditions in the WebRTC component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

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

A boundary condition vulnerability exists in the WebRTC component of Firefox and Thunderbird. Incorrect boundary checks in WebRTC could allow memory corruption or out-of-bounds access, potentially enabling arbitrary code execution or crash conditions. The issue was addressed in Firefox 150, Firefox ESR 115.35/140.10, and Thunderbird 150/140.10.

MitigationApply vendor patches by updating affected installations to Firefox 150 or later, Firefox ESR 115.35/140.10 or later, or Thunderbird 150/140.10 or later.

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:< 115.35.0< 150.0>= 140.0, < 140.10.0
ThunderbirdApplication
Affected:>= 140.0, < 140.10.0

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
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 checks

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

  1. Identify installed Mozilla product
    Check whether Firefox or Thunderbird is installed on the system. On Windows, look in Program Files/Mozilla Firefox or Program Files/Mozilla Thunderbird. On macOS, check /Applications/Firefox.app or /Applications/Thunderbird.app. On Linux, run 'which firefox' or 'which thunderbird'.
    Affected if The product is either Firefox or Thunderbird
  2. Determine Firefox version
    For Firefox: Enter 'about:support' in the address bar and look for 'Version' in the page, or run 'firefox --version' from command line.
    Affected if Version is < 115.35.0 OR (>= 115.35.0 AND < 140.10.0 AND < 150.0) OR (>= 140.0 AND < 140.10.0)
  3. Determine Thunderbird version
    For Thunderbird: Enter 'about:support' in the address bar and look for 'Version' in the page, or run 'thunderbird --version' from command line.
    Affected if Version is >= 140.0 AND < 140.10.0
  4. Confirm WebRTC is enabled
    In Firefox: Go to about:config and search for 'media.peerconnection.enabled'. In Thunderbird: Go to about:config and search for the same setting. Verify the boolean value is set to true.
    Affected if WebRTC is enabled (media.peerconnection.enabled = true)

The environment is affected if either Firefox version is < 115.35.0 OR < 150.0 (considering the 140.x branch), or Thunderbird version is >= 140.0 and < 140.10.0, AND WebRTC is enabled in the application settings.

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 115.35.0 / 140.10.0 / 150.0 or later
Fixed in 115.35.0140.10.0150.0
Interim mitigation

Apply vendor patches by updating affected installations to Firefox 150 or later, Firefox ESR 115.35/140.10 or later, or Thunderbird 150/140.10 or later.

Recommended fix High confidence

Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, or Thunderbird 140.10 (depending on current version branch)

  1. Identify the currently installed Firefox or Thunderbird version from the application menu (Help > About Firefox/Thunderbird)
  2. For Firefox users on versions < 115.35.0: Upgrade to Firefox ESR 115.35 or later
  3. For Firefox users on versions >= 140.0 and < 140.10.0: Upgrade to Firefox ESR 140.10 or later
  4. For Firefox users on versions < 150.0 (not covered by ESR paths above): Upgrade to Firefox 150 or later
  5. For Thunderbird users on versions >= 140.0 and < 140.10.0: Upgrade to Thunderbird 140.10 or later
  6. Restart the application after upgrading
  7. Verify the installed version from Help > About matches a fixed release
Caveat Standard Firefox/Thunderbird upgrades are backward compatible with profiles and extensions; no special migration steps required

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
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.

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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-2026-6752 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