What’s Vulnerable › Vulnerabilities

CVE-2019-9821

• Severity: high (CVSS 8.1 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-07-23 · updated 2026-06-17
• Weakness: CWE-362

Description

A use-after-free vulnerability can occur in AssertWorkerThread due to a race condition with shared workers. This results in a potentially exploitable crash. This vulnerability affects Firefox < 67.

Affected products

• Mozilla Firefox: before 67.0 — fixed in 67.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 67.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1539125
• https://www.mozilla.org/security/advisories/mfsa2019-13/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1539125
• https://www.mozilla.org/security/advisories/mfsa2019-13/

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