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FirefoxWeb browser · Mozilla

CVE-2026-6750

HIGH · 8.8 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 →
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
Privilege escalation in the Graphics: WebRender 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 privilege escalation vulnerability exists in Mozilla's WebRender graphics component, which is Firefox's GPU-based rendering engine. The vulnerability allows an attacker to elevate privileges, likely by exploiting how WebRender handles graphics operations or memory. The issue was addressed in the specified Firefox and Thunderbird versions.

MitigationApply the vendor-supplied updates: upgrade to Firefox 150+, Firefox ESR 115.35+, Firefox ESR 140.10+, Thunderbird 150+, or Thunderbird 140.10+ to remediate this vulnerability.

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:< 140.10.0

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
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. Identify installed Firefox version
    In Firefox, go to Menu > Help > About Firefox, or navigate to about:support in the address bar. The version number is displayed at the top.
    Affected if Version is below 115.35.0, or between 140.0 and 140.9.x, or below 150.0 (for standard release line)
  2. Identify installed Thunderbird version
    In Thunderbird, go to Menu > Help > About Thunderbird, or navigate to about:support in the address bar. The version number is displayed.
    Affected if Version is below 140.10.0
  3. Verify WebRender is enabled
    In Firefox, type about:support in the address bar and look for the 'Compositing' entry in the Graphics section. Alternatively, go to about:config and check the gfx.webrender.enabled preference (true means enabled).
    Affected if gfx.webrender.enabled is set to true (WebRender is active)
  4. Check graphics rendering backend
    In Firefox, navigate to about:support and locate the 'Graphics' section. Look for 'WebRender' listed as the compositor or rendering backend.
    Affected if WebRender is listed as the active renderer (not Basic or Skia)
  5. Confirm OS platform
    This vulnerability affects WebRender which is primarily active on Windows 10/11 and modern macOS versions. Check your operating system version via system settings or 'winver' on Windows.
    Affected if Running Windows 10/11 or modern macOS with WebRender enabled in affected Firefox/Thunderbird versions

User is affected if Firefox version is below 115.35.0, between 140.0-140.9.x, or below 150.0 (non-ESR), OR Thunderbird is below 140.10.0, AND WebRender is actively enabled as the graphics compositor.

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 the vendor-supplied updates: upgrade to Firefox 150+, Firefox ESR 115.35+, Firefox ESR 140.10+, Thunderbird 150+, or Thunderbird 140.10+ to remediate this vulnerability.

Recommended fix High confidence

Firefox 150 or Firefox ESR 115.35/140.10; Thunderbird 150 or Thunderbird 140.10 (depending on release channel)

  1. Check the current Firefox or Thunderbird version by navigating to Menu > Help > About (or using the menu bar)
  2. Download the appropriate fixed version from the official Mozilla website: Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, or Thunderbird 140.10
  3. Run the downloaded installer to apply the update
  4. Restart Firefox or Thunderbird after the installation completes
  5. Verify the version by checking Menu > Help > About to confirm the installation was successful

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.

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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-2026-6750 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