CVE-2019-9813

Q: How do I fix CVE-2019-9813?

Published advisories record a fix for 6 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Q: Is CVE-2019-9813 being actively exploited?

Not that we know of. CVE-2019-9813 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 6.3% is the estimated probability that it will be exploited in the next 30 days. That is higher than 93% of all scored CVEs.

Q: How severe is CVE-2019-9813?

CVE-2019-9813 has a CVSS v3 base score of 8.8, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2019-9813 affect?

Published advisories record a fix for firefox (Debian), firefox (Ubuntu), thunderbird (Ubuntu), DeveloperEdition (Windows application), and 2 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

HIGHEPSS 93th pctl

8.8

CVSS v3

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.

CWE-843Type Confusion

How to fix

Remediation Available

firefoxDebian

Fixed in:66.0.1-1CVE-2019-9813

firefoxUbuntu

Fixed in:66.0.1+build1-0ubuntu0.14.04.1USN-3919-1

Fixed in:66.0.1+build1-0ubuntu0.16.04.1USN-3919-1

Fixed in:66.0.1+build1-0ubuntu0.18.04.1USN-3919-1

thunderbirdUbuntu

Fixed in:1:60.6.1+build2-0ubuntu0.14.04.1USN-3927-1

Fixed in:1:60.6.1+build2-0ubuntu0.16.04.1USN-3927-1

Fixed in:1:60.6.1+build2-0ubuntu0.18.04.1USN-3927-1

DeveloperEditionWindows application

Affected:66.0.1Fixed in:66.0.1Mozilla

Affected:60.6.1Fixed in:60.6.1Mozilla

Mozilla Firefox (en-US)Windows application

Affected:60.6.1Fixed in:60.6.1Mozilla

Affected:66.0.1Fixed in:66.0.1Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:60.6.1Fixed in:60.6.1Mozilla

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

6.25%probability of exploitation in 30 days

93rdpercentile

High risk: more likely to be exploited than 93% of all known CVEs.

References

Vendor Advisory4

Other references2

Related Vulnerabilities

Other CWE-843 (Type Confusion) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2011-0611	High	8.8	99%	KEV	Fix
CVE-2012-0507	Critical	9.8	98%	KEV + Ransom	-
CVE-2017-8291	High	7.8	97%	KEV	Fix
CVE-2021-21224	High	8.8	84%	KEV	Fix
CVE-2019-0752	High	7.5	82%	KEV + Ransom	-
CVE-2017-0037	High	8.1	80%	KEV	-

Common questions

How do I fix CVE-2019-9813?

Published advisories record a fix for 6 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Is CVE-2019-9813 being actively exploited?

Not that we know of. CVE-2019-9813 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 6.3% is the estimated probability that it will be exploited in the next 30 days. That is higher than 93% of all scored CVEs.

How severe is CVE-2019-9813?

CVE-2019-9813 has a CVSS v3 base score of 8.8, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2019-9813 affect?

Published advisories record a fix for firefox (Debian), firefox (Ubuntu), thunderbird (Ubuntu), DeveloperEdition (Windows application), and 2 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-11-25.