dbcve.org
FirefoxWeb browser · Mozilla

CVE-2025-54143

CRITICAL · 9.8 CVSS v3.1 Published 2025-08-19
Fix available
A fix is available. Upgrade to 141.0 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
Sandboxed iframes on webpages could potentially allow downloads to the device, bypassing the expected sandbox restrictions declared on the parent page. This vulnerability was fixed in Firefox for iOS 141.

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

Firefox for iOS contains a sandbox bypass vulnerability where sandboxed iframes could initiate downloads to the device, contrary to the sandbox restrictions declared on the parent page. This allows potentially malicious web content to bypass intended download prevention controls.

MitigationUpdate Firefox for iOS to version 141 or later 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:< 141.0

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. Verify Firefox for iOS is installed
    Check the iOS device for the Firefox for iOS application in the app library or home screen
    Affected if Firefox for iOS is present on the device
  2. Check installed Firefox for iOS version
    Open the App Store app, tap your profile icon, tap Purchased, find Firefox for iOS, and note the version number displayed. Alternatively, open Firefox for iOS, go to Settings > About Firefox to see the version.
    Affected if The displayed version is any version prior to 141.0 (e.g., 140.0, 139.0, etc.)
  3. Confirm web content uses sandboxed iframes
    Review web pages served within Firefox for iOS for iframe elements with the sandbox attribute (e.g., <iframe sandbox="...">). Inspect the page source or use browser developer tools to identify any sandboxed iframe tags.
    Affected if The page contains sandboxed iframes and the browser version is below 141.0

A user is affected if Firefox for iOS version below 141.0 is installed and web content with sandboxed iframes is accessed, allowing downloads to bypass intended sandbox restrictions.

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 141.0 or later
Fixed in 141.0
Interim mitigation

Update Firefox for iOS to version 141 or later to remediate this vulnerability.

Recommended fix High confidence

Firefox for iOS 141.0

  1. Upgrade Firefox for iOS to version 141.0 or later through the iOS App Store or device update mechanism

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,090
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,744.

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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-2025-54143 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