CVE-2019-17026
Published 2020-03-02 · Updated 2026-06-17 · Source security@mozilla.org
Summary
CVE-2019-17026 is a high-severity (CVSS 8.8) vulnerability in Mozilla Firefox and Thunderbird. CISA added it to the Known Exploited Vulnerabilities catalog on November 3, 2021, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by May 3, 2022. CISA does not currently list it as used in ransomware campaigns. Mozilla has 13 vulnerabilities in the KEV catalog, 1 of them linked to ransomware.
All 13 known-exploited Mozilla vulnerabilities →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 vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CISA Known-Exploited Vulnerability
Product: Mozilla — Firefox and Thunderbird
Name: Mozilla Firefox And Thunderbird Type Confusion Vulnerability
Date added: 2021-11-03 · Due: 2022-05-03
Required action: Apply updates per vendor instructions.
References
- http://packetstormsecurity.com/files/162568/Firefox-72-IonMonkey-JIT-Type-Confusion.html
- https://bugzilla.mozilla.org/show_bug.cgi?id=1607443
- https://security.gentoo.org/glsa/202003-02
- https://usn.ubuntu.com/4335-1/
- https://www.mozilla.org/security/advisories/mfsa2020-03/
- https://www.mozilla.org/security/advisories/mfsa2020-04/
- http://packetstormsecurity.com/files/162568/Firefox-72-IonMonkey-JIT-Type-Confusion.html
- https://bugzilla.mozilla.org/show_bug.cgi?id=1607443

