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FirefoxWeb browser · Mozilla

CVE-2019-9796

CRITICAL · 9.8 CVSS v3.0 Published 2019-04-26
Fix available
A fix is available. Upgrade to 60.6.0 / 66.0 or later.
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
A use-after-free vulnerability can occur when the SMIL animation controller incorrectly registers with the refresh driver twice when only a single registration is expected. When a registration is later freed with the removal of the animation controller element, the refresh driver incorrectly leaves a dangling pointer to the driver's observer array. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.

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 the SMIL animation controller where incorrect double registration with the refresh driver leaves a dangling pointer to the driver's observer array after the animation controller element is removed, allowing potential memory corruption and arbitrary code execution.

MitigationUpgrade to Firefox 66+, Firefox ESR 60.6+, or Thunderbird 60.6+ to remediate this critical 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:< 60.6.0< 66.0
ThunderbirdApplication
Affected:< 60.6.0

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
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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. Identify installed Mozilla product
    Check for Firefox or Thunderbird installation. On Windows, look in Program Files; on macOS, check /Applications; on Linux, check package manager or which firefox thunderbird
    Affected if Neither Firefox nor Thunderbird is installed, or neither is a relevant product type for this environment
  2. Determine Firefox version
    In Firefox, go to Help > About Firefox, or run: firefox --version (Linux/macOS) or check the executable properties (Windows)
    Affected if Firefox version is less than 60.6.0 or falls between 60.6.0 and 66.0 (non-inclusive of 66.0)
  3. Determine Thunderbird version
    In Thunderbird, go to Help > About Thunderbird, or run: thunderbird --version (Linux/macOS) or check the executable properties (Windows)
    Affected if Thunderbird version is less than 60.6.0
  4. Assess SMIL animation usage
    Inspect web content or applications loaded in the browser for use of SMIL (<animate>, <animateTransform>, <set> elements in SVG). Check browser console for SMIL-related warnings or errors during animation playback
    Affected if SMIL animations are actively used in content while running an affected browser version, triggering the vulnerable code path in the animation controller
  5. Verify refresh driver interaction
    This is a code-level internal condition. Check if the browser has been used to view content with animated SVGs that get removed from the DOM while animating
    Affected if The browser with an affected version has displayed and interacted with animated SVG content that was dynamically removed during animation playback, triggering the double-registration flaw

A system is affected if Firefox (any version below 60.6.0 or between 60.6.0 and 65.x) or Thunderbird (any version below 60.6.0) is installed and the browser has been used to render SMIL-based SVG animations that were removed during playback.

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
Upgrade available Upgrade to 60.6.0 / 66.0 or later
Fixed in 60.6.066.0
Interim mitigation

Upgrade to Firefox 66+, Firefox ESR 60.6+, or Thunderbird 60.6+ to remediate this critical vulnerability.

Recommended fix High confidence

Firefox 66.0 or later (or Firefox ESR 60.6.0+); Thunderbird 60.6.0 or later

  1. Identify the installed Firefox or Thunderbird version by navigating to Help > About in the application menu
  2. For Firefox: Upgrade to version 66.0 or later (or Firefox ESR 60.6.0 or later if using ESR)
  3. For Thunderbird: Upgrade to version 60.6.0 or later
  4. Restart the application after upgrade to ensure the new version is fully active
  5. Verify the version after restart by checking Help > About to confirm the patched version is installed
Caveat Mozilla releases typically include backward-compatible updates; verify critical add-ons are compatible with the new version before deployment in production environments

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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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-2019-9796 in production — separate from our analysis above.

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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