What’s Vulnerable › Vulnerabilities

CVE-2019-9791

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 19.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2019-04-26 · updated 2026-06-17
• Weakness: CWE-843

Description

The type inference system allows the compilation of functions that can cause type confusions between arbitrary objects when compiled through the IonMonkey just-in-time (JIT) compiler and when the constructor function is entered through on-stack replacement (OSR). This allows for possible arbitrary reading and writing of objects during an exploitable crash. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.

Affected products

• Mozilla Firefox: before 60.6.0; before 66.0 — fixed in 60.6.0, 66.0
• Mozilla Thunderbird: before 60.6.0 — fixed in 60.6.0
• Red Hat Enterprise Linux: 8.0
• RedHat Enterprise Linux Eus: 8.1, 8.2, 8.4
• RedHat Enterprise Linux Server Aus: 8.2, 8.4
• RedHat Enterprise Linux Server Tus: 8.2, 8.4

How to fix

Upgrade to a fixed version: Mozilla Firefox 60.6.0, 66.0; Mozilla Thunderbird 60.6.0. Check the vendor advisory for mitigations.

References

• https://access.redhat.com/errata/RHSA-2019:0966
• https://access.redhat.com/errata/RHSA-2019:1144
• https://bugzilla.mozilla.org/show_bug.cgi?id=1530958
• https://www.mozilla.org/security/advisories/mfsa2019-07/
• https://www.mozilla.org/security/advisories/mfsa2019-08/
• https://www.mozilla.org/security/advisories/mfsa2019-11/
• https://access.redhat.com/errata/RHSA-2019:0966
• https://access.redhat.com/errata/RHSA-2019:1144
• https://bugzilla.mozilla.org/show_bug.cgi?id=1530958
• https://www.mozilla.org/security/advisories/mfsa2019-07/
• https://www.mozilla.org/security/advisories/mfsa2019-08/
• https://www.mozilla.org/security/advisories/mfsa2019-11/

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