CVE-2019-9791

Name: CVE-2019-9791
Creator: NVD / NIST
Published: 2019-04-26T17:29:01.523+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 19.76%

Last modified Jun 17, 2026

CVE-2019-9791 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. EPSS estimates a 19.76% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

19.76%

97.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-843

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 60.6.0
Mozilla	Firefox	< 66.0
Mozilla	Thunderbird	< 60.6.0
Redhat	Enterprise Linux	8.0
Redhat	Enterprise Linux Eus	8.1
Redhat	Enterprise Linux Eus	8.2
Redhat	Enterprise Linux Eus	8.4
Redhat	Enterprise Linux Server Aus	8.2
Redhat	Enterprise Linux Server Aus	8.4
Redhat	Enterprise Linux Server Tus	8.2
Redhat	Enterprise Linux Server Tus	8.4

References

https://access.redhat.com/errata/RHSA-2019:0966Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1144Third Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1530958Exploit, Issue Tracking, Vendor 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
https://access.redhat.com/errata/RHSA-2019:0966Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1144Third Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1530958Exploit, Issue Tracking, Vendor 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

Timeline

Published: Apr 26, 2019
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2019-9791?

How severe is CVE-2019-9791?

CVE-2019-9791 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 19.76% probability of exploitation in the next 30 days.

How do I fix CVE-2019-9791?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2019-9791?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST