What’s Vulnerable › Vulnerabilities

CVE-2019-9820

• Severity: critical (CVSS 9.8 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.6% 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-416

Description

A use-after-free vulnerability can occur in the chrome event handler when it is freed while still in use. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 60.7, Firefox < 67, and Firefox ESR < 60.7.

Affected products

• Mozilla Firefox: before 67.0 — fixed in 67.0
• Mozilla Firefox ESR: before 60.7 — fixed in 60.7
• Mozilla Thunderbird: before 60.7.0 — fixed in 60.7.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 67.0; Mozilla Firefox ESR 60.7; Mozilla Thunderbird 60.7.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1536405
• https://www.mozilla.org/security/advisories/mfsa2019-13/
• https://www.mozilla.org/security/advisories/mfsa2019-14/
• https://www.mozilla.org/security/advisories/mfsa2019-15/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1536405
• https://www.mozilla.org/security/advisories/mfsa2019-13/
• https://www.mozilla.org/security/advisories/mfsa2019-14/
• https://www.mozilla.org/security/advisories/mfsa2019-15/

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