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FirefoxWeb browser · Mozilla

CVE-2015-7193

HIGH · 7.5 CVSS v2.0 Published 2015-11-05
Fix available
A fix is available. Upgrade to after 41.0.2 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
Mozilla Firefox before 42.0 and Firefox ESR 38.x before 38.4 improperly follow the CORS cross-origin request algorithm for the POST method in situations involving an unspecified Content-Type header manipulation, which allows remote attackers to bypass the Same Origin Policy by leveraging the lack of a preflight-request step.

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 42.0 and Firefox ESR 38.x before 38.4 fail to properly enforce the CORS cross-origin request algorithm for POST requests when the Content-Type header is manipulated or unspecified, allowing attackers to bypass the Same Origin Policy without triggering the required preflight request.

MitigationUpdate Mozilla Firefox to version 42.0 or later, or Firefox ESR to version 38.4 or later, to obtain the vendor patch for this CORS bypass 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:= 38.0= 38.0.1= 38.0.5= 38.1.0= 38.1.1= 38.2.0= 38.2.1= 38.3.0<= 41.0.2

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
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
Partial

AV:N/AC:L/Au:N/C:P/I:P/A:P

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 installed Firefox version
    Navigate to Firefox menu > Help > About Firefox, or enter 'about:support' in the address bar, or run 'firefox --version' from command line
    Affected if The displayed version is earlier than 42.0 for standard Firefox, or earlier than 38.4 for Firefox ESR
  2. Identify Firefox ESR version
    In about:support, look for 'Application Update' section or check 'Version' field in the general section; ESR versions typically end with 'esr'
    Affected if Version shows '38.x esr' where x is less than 4 (e.g., 38.0, 38.1, 38.2, 38.3)
  3. Inspect web traffic for cross-origin POST requests
    Open Developer Tools (F12), go to Network tab, and monitor for POST requests to different domains; check for requests with Content-Type header missing or non-standard values (not application/x-www-form-urlencoded, multipart/form-data, or text/plain)
    Affected if Cross-origin POST requests are observed without a preceding OPTIONS preflight request, indicating the browser may not be enforcing CORS correctly

A user is affected if they are running Firefox versions earlier than 42.0 (or Firefox ESR earlier than 38.4) AND their browser is used to interact with web applications making cross-origin POST requests with manipulated or unspecified Content-Type headers.

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 41.0.2
Interim mitigation

Update Mozilla Firefox to version 42.0 or later, or Firefox ESR to version 38.4 or later, to obtain the vendor patch for this CORS bypass vulnerability.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

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-2015-7193 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
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