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CVE-2019-17026

Mozilla Firefox And Thunderbird Type Confusion

8.8 HIGHActively exploited (CISA KEV)Public exploitEPSS 46.3%
  1. Published2 Mar 2020
  2. Added to CISA KEV3 Nov 2021
  3. Remediation due3 May 2022
Actively exploited (CISA KEV)

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

Added to KEV: 3 Nov 2021Federal remediation due: 3 May 2022

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionRequired
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

Mozilla Firefox< 72.0.1 · < 68.4.1
Mozilla Thunderbird< 68.4.1
Canonical Ubuntu Linux16.04

Remediation

Fixed in
Mozilla Firefox≥ 72.0.1
Mozilla Thunderbird≥ 68.4.1

References

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Frequently asked

Is CVE-2019-17026 being actively exploited?

Yes. CVE-2019-17026 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 3 Nov 2021.

How severe is CVE-2019-17026?

CVE-2019-17026 has a CVSS 3.1 base score of 8.8, rated high. EPSS estimates a 46.3% probability of exploitation.

Which products are affected by CVE-2019-17026?

Affected products include Mozilla Firefox, Mozilla Thunderbird, Canonical Ubuntu Linux.

How do I fix CVE-2019-17026?

Upgrade affected software to a fixed version, for example Mozilla Firefox 72.0.1, Mozilla Thunderbird 68.4.1 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2019-17026 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.