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CVE-2019-17026

Mozilla Firefox And Thunderbird Type Confusion Vulnerability

  • High 8.8
  • Exploited: added to CISA KEV 3 Nov 2021

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.

Key facts

Published
2 Mar 2020
Last changed
21 Oct 2025
Assigned by
mozilla
KEV added
3 Nov 2021
KEV fix due
3 May 2022
EPSS
46.311% likely to be exploited in the next 30 days, higher than 98.838% of CVEs (scores for 15 Nov 2026)
SSVC (CISA)
Exploitation: active; Automatable: no; Technical impact: total

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

  • 8.8CVSS 3.1, Highfrom CISA (ADP container)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

What to do

  • Apply updates per vendor instructions.CISA KEV required action

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

VendorProductVersions
MozillaFirefox ESR
  • unspecified up to but excluding 68.4.1 (affected)
MozillaThunderbird
  • unspecified up to but excluding 68.4.1 (affected)
MozillaFirefox
  • unspecified up to but excluding 72.0.1 (affected)

Timeline

  1. 2 Mar 2020 Published
  2. 3 Nov 2021 CVE-2019-17026 added to CISA KEV
  3. 3 Nov 2021 Added to the CISA KEV catalogue

Weakness

References