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FirefoxWeb browser · Mozilla

CVE-2015-4497

HIGH · 10.0 CVSS v2.0 Published 2015-08-29
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
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
Use-after-free vulnerability in the CanvasRenderingContext2D implementation in Mozilla Firefox before 40.0.3 and Firefox ESR 38.x before 38.2.1 allows remote attackers to execute arbitrary code by leveraging improper interaction between resize events and changes to Cascading Style Sheets (CSS) token sequences for a CANVAS element.

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

Use-after-free vulnerability in Mozilla Firefox's CanvasRenderingContext2D implementation allows remote attackers to execute arbitrary code by leveraging improper interaction between resize events and changes to Cascading Style Sheets (CSS) token sequences for a CANVAS element.

MitigationUpgrade to Firefox 40.0.3 or later (or Firefox ESR 38.2.1 or later) to obtain the vendor patch; alternatively, deploy the available security update from Mozilla.

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= 38.2.0= 40.0.2

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
Complete
Integrity
Complete
Availability
Complete

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

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. Determine installed Firefox version
    Open Firefox, click the menu button (three horizontal lines), select Help, then About Firefox. The version number will be displayed on the page that opens.
    Affected if The displayed version matches any of the following: 38.0, 38.0.1, 38.0.5, 38.1.0, 38.2.0, or 40.0.2
  2. Verify version via command line (if available)
    Run 'firefox --version' from a terminal or command prompt. On Windows, you can also check 'C:\Program Files\Mozilla Firefox\firefox.exe' properties for version info.
    Affected if The version output matches any of the affected versions listed above
  3. Confirm CanvasRenderingContext2D is in use
    This is a built-in HTML5 canvas feature. If the browser can render web pages with canvas elements, this component is active. No configuration toggle exists for it.
    Affected if The browser can render canvas elements at all - this confirms the vulnerable code path exists in the affected versions

A user is affected if their installed Firefox version is exactly 38.0, 38.0.1, 38.0.5, 38.1.0, 38.2.0, or 40.0.2, as these versions contain the vulnerable CanvasRenderingContext2D implementation.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Firefox 40.0.3 or later (or Firefox ESR 38.2.1 or later) to obtain the vendor patch; alternatively, deploy the available security update from Mozilla.

Recommended fix High confidence

Firefox 40.0.3 or later (standard release), or Firefox ESR 38.2.1 or later (ESR branch)

  1. Identify the currently installed Firefox version by navigating to Help > About Firefox
  2. Download Firefox 40.0.3 or later from the official Mozilla website (www.mozilla.org) or use your system's package manager
  3. If using Firefox ESR 38.x, upgrade to Firefox ESR 38.2.1 or later instead
  4. Restart Firefox after the update to complete the installation
  5. Verify the update was successful by checking Help > About Firefox shows version 40.0.3+ or ESR 38.2.1+

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2015-4497 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