CVE-2019-17026

KEVMozilla Firefox And Thunderbird Type Confusion Vulnerability

Description

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

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

PublishedMar 2, 2020

Last modifiedJun 17, 2026

Added to KEVNov 3, 2021

Remediation dueMay 3, 2022

References

packetstormsecurity.com/files/162568/Firefox-72-IonMonkey-JIT-Type-Confusion.htmlExploitThird Party Advisory
bugzilla.mozilla.org/show_bug.cgi?id=1607443Issue Tracking
security.gentoo.org/glsa/202003-02Third Party Advisory
usn.ubuntu.com/4335-1/Third Party Advisory
mozilla.org/security/advisories/mfsa2020-03/Vendor Advisory
mozilla.org/security/advisories/mfsa2020-04/Vendor Advisory
cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2019-17026US Government Resource

0 recent articles mention this CVE

Risk assessment · High

Actively exploited. Patch immediately.

Exploitation: Confirmed in the wild (CISA KEV)
Federal remediation deadline: Overdue by 1637 days
CVSS: 8.8 HIGH
EPSS (30-day exploit probability): 46.3% · top 1% of all CVEs
Weakness: CWE-843
Attack vector: Network, remotely reachable

Recommended actions

1.Apply updates per vendor instructions.
2.Treat as emergency change: patch or isolate internet-facing instances first.
3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.

Assessment is derived automatically from the live signals above; verify against your own asset inventory.