dbcve.org
Firefox MobileWeb browser · Mozilla

CVE-2020-26975

MEDIUM · 6.5 CVSS v3.1 Published 2021-01-07
Fix available
A fix is available. Upgrade to 84.0 or later.
See remediation →
72/100
Remediation priority · Elevated
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
When a malicious application installed on the user's device broadcast an Intent to Firefox for Android, arbitrary headers could have been specified, leading to attacks such as abusing ambient authority or session fixation. This was resolved by only allowing certain safe-listed headers. *Note: This issue only affected Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects Firefox < 84.

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 Android versions prior to 84 contained a vulnerability in Intent handling where a malicious application installed on the device could broadcast Intents containing arbitrary HTTP headers to the browser. This allowed attackers to perform session fixation attacks by injecting session cookies via headers, or abuse ambient authority by specifying authentication headers that the browser would unknowingly use.

MitigationUpgrade Firefox for Android to version 84 or later, which implements a safe-list restricting which headers can be set via Intent broadcasts. For organizations unable to upgrade immediately, advise users to only install applications from trusted sources.

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
Firefox MobileWeb browser
Affected:< 84.0

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
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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. Check if Firefox for Android is installed
    Run 'pm list packages | grep -i firefox' or 'pm list packages -3 | grep mozilla' to list installed Firefox packages
    Affected if Any Firefox package from Mozilla is installed (e.g., org.mozilla.firefox, org.mozilla.firefox_beta)
  2. Retrieve the installed Firefox version
    Run 'dumpsys package <package_name>' replacing <package_name> with the Firefox package found (e.g., org.mozilla.firefox), then locate the 'versionName' field under the 'Package:' section
    Affected if The versionName field shows a version number lower than 84.0 (e.g., 83.1.2, 83.0.1, etc.)
  3. Verify the exact version number against the affected range
    Compare the version number found to the affected range: any version prior to 84.0 (versions 83.x, 82.x, 81.x, etc.)
    Affected if The installed version is 83.x or any earlier major version (e.g., 83.0, 83.0.1, 82.0)
  4. Confirm this is the Android browser variant
    Ensure the package name indicates Firefox for Android (org.mozilla.firefox) rather than Firefox for desktop or other Mozilla products
    Affected if The affected package is org.mozilla.firefox (standard) or org.mozilla.firefox_beta (beta) on versions below 84.0

A user is affected if Firefox for Android is installed with a version prior to 84.0, as this version introduced the header safe-list mitigation for Intent broadcasts.

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 84.0 or later
Fixed in 84.0
Interim mitigation

Upgrade Firefox for Android to version 84 or later, which implements a safe-list restricting which headers can be set via Intent broadcasts. For organizations unable to upgrade immediately, advise users to only install applications from trusted sources.

Fix this in Firefox Mobile Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,880
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,808.

Scan for this in your stack

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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-2020-26975 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