What’s Vulnerable › Vulnerabilities

CVE-2019-9800

• Severity: critical (CVSS 9.8 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% 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-787

Description

Mozilla developers and community members reported memory safety bugs present in Firefox 66, Firefox ESR 60.6, and Thunderbird 60.6. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code. 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 — fixed in 60.7

How to fix

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

References

• https://bugzilla.mozilla.org/buglist.cgi?bug_id=1540166%2C1534593%2C1546327%2C1540136%2C1538736%2C1538042%2C1535612%2C1499719%2C1499108%2C1538619%2C1535194%2C1516325%2C1542324%2C1542097%2C1532465%2C1533554%2C1541580
• 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/buglist.cgi?bug_id=1540166%2C1534593%2C1546327%2C1540136%2C1538736%2C1538042%2C1535612%2C1499719%2C1499108%2C1538619%2C1535194%2C1516325%2C1542324%2C1542097%2C1532465%2C1533554%2C1541580
• 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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