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Vulnerability record · CVE-2019-9792 · published 26 April 2019

CVE-2019-9792: Mozilla firefox out-of-bounds write vulnerability

Mozilla · Firefox

The IonMonkey just-in-time (JIT) compiler can leak an internal JS_OPTIMIZED_OUT magic value to the running script during a bailout. This magic value can then be used by JavaScript to achieve memory corruption, which results in a potentially exploitable crash. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.

9.8 CVSS 3.1 Critical EPSS 13% · top 3.8% CWE-787 · Out-of-bounds write
9.8CVSS 3.1 base score, v2 7.5
13%EPSS exploitation probability, 30 days
NoNot in CISA KEV
6Affected product versions listed by NVD
14References, 4 tagged exploit
17 Jun 2026Last modified by NVD

Description

The IonMonkey just-in-time (JIT) compiler can leak an internal JS_OPTIMIZED_OUT magic value to the running script during a bailout. This magic value can then be used by JavaScript to achieve memory corruption, which results in a potentially exploitable crash. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

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

References

LinkTags
http://packetstormsecurity.com/files/153106/Spidermonkey-IonMonkey-JS_OPTIMIZED_OUT-Value-Leak.html ExploitThird Party AdvisoryVDB Entry
https://access.redhat.com/errata/RHSA-2019:0966 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1144 Third Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1532599 ExploitIssue TrackingVendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-07/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-08/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-11/ Vendor Advisory
http://packetstormsecurity.com/files/153106/Spidermonkey-IonMonkey-JS_OPTIMIZED_OUT-Value-Leak.html ExploitThird Party AdvisoryVDB Entry
https://access.redhat.com/errata/RHSA-2019:0966 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1144 Third Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1532599 ExploitIssue TrackingVendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-07/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-08/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2019-11/ 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-2019-9792), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.