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FirefoxWeb browser · Mozilla

CVE-2016-2827

MEDIUM · 6.5 CVSS v3.0 Published 2016-09-22
Fix available
A fix is available. Upgrade to after 48.0.2 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
The mozilla::net::IsValidReferrerPolicy function in Mozilla Firefox before 49.0 allows remote attackers to cause a denial of service (out-of-bounds read and application crash) via a Content Security Policy (CSP) referrer directive with zero values.

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

Mozilla Firefox before 49.0 contains an out-of-bounds read vulnerability in the mozilla::net::IsValidReferrerPolicy function when parsing Content Security Policy (CSP) referrer directives containing zero values, leading to application crash and denial of service.

MitigationUpgrade Firefox to version 49.0 or later to obtain the patched version of the IsValidReferrerPolicy function that properly handles zero values in CSP referrer directives.

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:<= 48.0.2

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
None
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/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. Check Firefox version number
    Open the URL 'about:firefox' in the browser address bar, or go to Help > About Firefox, to display the installed version
    Affected if Version shown is 48.0.2 or any earlier version (versions below 49.0)
  2. Identify CSP referrer policy in use
    Inspect web application HTTP response headers for 'Content-Security-Policy' header containing a 'referrer' directive, or check HTML meta tags for <meta http-equiv='Content-Security-Policy' content='...referrer...'>
    Affected if Any Content Security Policy with a referrer directive is configured and the browser version is vulnerable
  3. Verify referrer directive contains zero values
    Review the CSP policy string - look for referrer directive values like 'no-referrer', 'never', empty string, or any non-standard referrer policy keyword that may evaluate to zero
    Affected if The referrer directive contains values that could be parsed as zero, combined with a vulnerable Firefox version

Environment is affected if Firefox version is 48.0.2 or earlier AND Content Security Policy with a referrer directive is being processed by the browser.

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 a release after 48.0.2
Interim mitigation

Upgrade Firefox to version 49.0 or later to obtain the patched version of the IsValidReferrerPolicy function that properly handles zero values in CSP referrer directives.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,696.

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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-2016-2827 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