CVE-2019-9821: Race Condition

Published May 21, 2019
·
Updated

A use-after-free vulnerability can occur in AssertWorkerThread due to a race condition with shared workers. This results in a potentially exploitable crash.

Affected Software

3 affected componentsFixes available
Mozilla Firefox<67
67
Mozilla Firefox<67.0
debian/firefox
154.0.1-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 67
  2. Upgrade

    Upgrade debian/firefox to a version that resolves this vulnerability.

    Fixed in 154.0.1-1

Event History

May 21, 2019
CVE Published
12:00 AM
Jul 23, 2019
CVE Published
via MITRE·01:23 PM
Data Sourced
via MITRE·01:23 PM
DescriptionWeakness
Data Sourced
via NVD·02:15 PM
DescriptionSeverityWeaknessAffected Software
Jan 11, 2024
Data Sourced
via Launchpad·11:34 PM
Description
Feb 19, 2026
Data Sourced
via Ubuntu·06:02 PM
RemedyDescriptionSeverityAffected Software
Aug 27, 2026
Data Sourced
via Debian·12:30 AM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Frequently Asked Questions

1

What is CVE-2019-9821?

CVE-2019-9821 is a use-after-free vulnerability that can occur in AssertWorkerThread due to a race condition with shared workers.

2

How does CVE-2019-9821 affect Firefox?

CVE-2019-9821 affects Firefox versions prior to 67.

3

What is the severity of CVE-2019-9821?

CVE-2019-9821 has a severity score of 8.1, which is considered high.

4

How can I fix CVE-2019-9821?

To fix CVE-2019-9821, update Firefox to version 67 or later.

5

Where can I find more information about CVE-2019-9821?

You can find more information about CVE-2019-9821 on the following references: [Bugzilla](https://bugzilla.mozilla.org/show_bug.cgi?id=1539125), [Mozilla Security Advisories](https://www.mozilla.org/en-US/security/advisories/mfsa2019-13/)

Contact

SecAlerts Pty Ltd.
132 Wickham Terrace
Fortitude Valley,
QLD 4006, Australia
info@secalerts.co
By using SecAlerts services, you agree to our services end-user license agreement. This website is safeguarded by reCAPTCHA and governed by the Google Privacy Policy and Terms of Service. All names, logos, and brands of products are owned by their respective owners, and any usage of these names, logos, and brands for identification purposes only does not imply endorsement. If you possess any content that requires removal, please get in touch with us.
© 2026 SecAlerts Pty Ltd.
ABN: 70 645 966 203, ACN: 645 966 203