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Vulnerability record · CVE-2019-9813 · published 26 April 2019

CVE-2019-9813: Mozilla firefox type confusion vulnerability

Mozilla · Firefox

Incorrect handling of __proto__ mutations may lead to type confusion in IonMonkey JIT code and can be leveraged for arbitrary memory read and write. This vulnerability affects Firefox < 66.0.1, Firefox ESR < 60.6.1, and Thunderbird < 60.6.1.

8.8 CVSS 3.0 High EPSS 7.4% · top 5.8% CWE-843 · Type confusion
8.8CVSS 3.0 base score, v2 6.8
7.4%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
12References
17 Jun 2026Last modified by NVD

Description

Incorrect handling of __proto__ mutations may lead to type confusion in IonMonkey JIT code and can be leveraged for arbitrary memory read and write. This vulnerability affects Firefox < 66.0.1, Firefox ESR < 60.6.1, and Thunderbird < 60.6.1.

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://access.redhat.com/errata/RHSA-2019:0966
https://access.redhat.com/errata/RHSA-2019:1144
https://bugzilla.mozilla.org/show_bug.cgi?id=1538006 Issue TrackingPermissions RequiredVendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-09/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-10/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-12/ Vendor Advisory
https://access.redhat.com/errata/RHSA-2019:0966
https://access.redhat.com/errata/RHSA-2019:1144
https://bugzilla.mozilla.org/show_bug.cgi?id=1538006 Issue TrackingPermissions RequiredVendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-09/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-10/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-12/ Vendor Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2019-9813), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.