FirefoxWeb browser · Mozilla
CVE-2015-7211
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 · uneditedMozilla Firefox before 43.0 mishandles the # (number sign) character in a data: URI, which allows remote attackers to spoof web sites via unspecified vectors.
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 confidenceMozilla Firefox before version 43.0 improperly processes the # (number sign) character within data: URIs, allowing attackers to craft malicious data: URLs that display as legitimate websites in the address bar. This URL spoofing vulnerability could trick users into trusting malicious content by misrepresenting the page's origin.
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
<= 42.0
FedoraOperating system
= 22= 23= 42.1= 13.1= 13.2CVSS 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
- Authentication
- None
- Confidentiality
- None
- Integrity
- Partial
- Availability
- None
AV:N/AC:L/Au:N/C:N/I:P/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 checksWork through these to decide whether this CVE applies to you.
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Identify installed Firefox versionOpen Firefox, go to Help > About Firefox, or run 'firefox --version' from command lineAffected if version displayed is 42.0 or lower
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Check Firefox package version on FedoraRun 'rpm -q firefox' on Fedora 22 or 23 systemsAffected if package version is 42.x or lower
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Check Firefox package version on openSUSERun 'rpm -q firefox' on openSUSE 13.1, 13.2, or Leap 42.1Affected if package version is 42.x or lower
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Verify data: URI handling behaviorCreate a test data: URI with a # fragment (e.g., data:text/html,<h1>Test#<script>alert(1)</script>) and observe how Firefox parses the URL in the address barAffected if the portion after # appears in address bar as part of the page content rather than being properly recognized as a fragment identifier
A system is affected if the installed Firefox version is 42.0 or lower, or if the browser displays misleading content in data: URIs containing the # character.
Generated from the published advisory. Verify against your own configuration.
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 dataUpdate Mozilla Firefox to version 43.0 or later to resolve the data: URI parsing issue. Organizations should ensure automated browser update mechanisms are enabled or deploy the updated version via endpoint management tools.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2015-7211 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2015-7211 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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
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