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FirefoxWeb browser · Mozilla

CVE-2020-6830

HIGH · 7.5 CVSS v3.1 Published 2020-05-26
Fix available
A fix is available. Upgrade to 25.0 or later.
See remediation →
84/100
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
For native-to-JS bridging, the app requires a unique token to be passed that ensures non-app code can't call the bridging functions. That token was being used for JS-to-native also, but it isn't needed in this case, and its usage was also leaking this token. This vulnerability affects Firefox for iOS < 25.

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 used a unique security token for native-to-JS bridging to prevent non-app code from calling native functions. This token was incorrectly also used for JS-to-native bridging (where it's not needed), causing the token to leak. An attacker could potentially capture this leaked token and use it to invoke native-to-JS bridging functions.

MitigationUpgrade Firefox for iOS to version 25 or later, which removes the unnecessary token from JS-to-native bridging and eliminates the token leakage.

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:< 25.0

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
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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. Confirm Firefox for iOS is installed
    Locate the Firefox browser app on your iOS device (iPhone/iPad). Check if the app with the Firefox logo is present in your app library or home screen.
    Affected if Firefox for iOS app exists on the device
  2. Identify the installed Firefox for iOS version
    Open the iOS Settings app, scroll to Firefox, and tap on it to view the version number. Alternatively, open the App Store, go to your purchased apps, and find Firefox for iOS to see the installed version.
    Affected if Version displayed is below 25.0 (e.g., 24.x, 23.x, etc.)
  3. Verify version against affected range
    Compare the installed version number you found against the affected range of versions less than 25.0.
    Affected if Installed version is any version prior to 25.0 (e.g., 24.0, 23.1, 22.0, etc.)

You are affected if Firefox for iOS is installed and its version is below 25.0, as the token leakage vulnerability exists in those earlier versions.

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.

From vendor data
Upgrade available Upgrade to 25.0 or later
Fixed in 25.0
Interim mitigation

Upgrade Firefox for iOS to version 25 or later, which removes the unnecessary token from JS-to-native bridging and eliminates the token leakage.

Fix this in Firefox Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.

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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-2020-6830 in production — separate from our analysis above.

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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