Is CVE-2019-9813 in the CISA KEV catalog?

No. CVE-2019-9813 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2019-9813?

CVE-2019-9813 has a CVSS v3 base score of 8.8 (HIGH).

What is the EPSS score for CVE-2019-9813?

CVE-2019-9813 has an EPSS score of 7.39% (94th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2019-9813?

Upgrade firefox on debian unstable to 66.0.1-1 or later. Fixes are available for 6 affected products.

CVE & CISA-KEV Catalog

CVE-2019-9813

HIGHEPSS 94th 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:66.0.1Fixed in:66.0.1Mozilla

Affected:60.6.1Fixed in:60.6.1Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:60.6.1Fixed in:60.6.1Mozilla

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

7.39%probability of exploitation in 30 days

94thpercentile

High risk: more likely to be exploited than 94% of all known CVEs.

References

Vendor Advisory4

Other references2

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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.