CVE-2019-17026

Q: How do I fix CVE-2019-17026?

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-2019-17026 being actively exploited?

Yes. CVE-2019-17026 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. US federal agencies were required to remediate it by 2022-05-03. Treat it as a priority whatever its CVSS score says.

Q: How severe is CVE-2019-17026?

CVE-2019-17026 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-2019-17026 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.

HIGHCISA KEVEPSS 99th pctl

8.8

CVSS v3

NVD

Description

Incorrect alias information in IonMonkey JIT compiler for setting array elements could lead to a type confusion. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Firefox ESR < 68.4.1, Thunderbird < 68.4.1, and Firefox < 72.0.1.

CWE-843Type Confusion

How to fix

Remediation Available

firefoxDebian

Fixed in:72.0.1-1CVE-2019-17026

firefoxUbuntu

Fixed in:72.0.1+build1-0ubuntu0.16.04.1USN-4234-1

Fixed in:72.0.1+build1-0ubuntu0.18.04.1USN-4234-1

thunderbirdUbuntu

Fixed in:1:68.7.0+build1-0ubuntu0.16.04.2USN-4335-1

Fixed in:1:68.4.1+build1-0ubuntu0.18.04.1USN-4241-1

DeveloperEditionWindows application

Affected:68.4.1Fixed in:68.4.1Mozilla

Affected:72.0.1Fixed in:72.0.1Mozilla

Mozilla Firefox (en-US)Windows application

Affected:68.4.1Fixed in:68.4.1Mozilla

Affected:72.0.1Fixed in:72.0.1Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:68.4.1Fixed in:68.4.1Mozilla

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

Exploit Intelligence

46.59%probability of exploitation in 30 days

99thpercentile

Very high risk: more likely to be exploited than 99% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

Mozilla Firefox And Thunderbird Type Confusion Vulnerability

Mozilla Firefox and Thunderbird contain a type confusion vulnerability due to incorrect alias information in the IonMonkey JIT compiler when setting array elements.

Apply updates per vendor instructions.

Remediation due: 2022-05-03

References

Exploit1

packetstormsecurity.com

Vendor Advisory2

Third-Party Advisory2

Government Resource1

cisa.gov

Issue Tracking1

bugzilla.mozilla.org

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-2019-17026?

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-2019-17026 being actively exploited?

Yes. CVE-2019-17026 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. US federal agencies were required to remediate it by 2022-05-03. Treat it as a priority whatever its CVSS score says.

How severe is CVE-2019-17026?

CVE-2019-17026 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-2019-17026 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 2025-11-04.