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Remote code execution in Mozilla Firefox and Firefox ESR

Published: 2020-01-08
Severity Critical
Patch available YES
Number of vulnerabilities 1
CVE ID CVE-2019-17026
Exploitation vector Network
Public exploit This vulnerability is being exploited in the wild.
Vulnerable software
Mozilla Firefox
Client/Desktop applications / Web browsers

Firefox ESR
Client/Desktop applications / Web browsers

Vendor Mozilla

Security Advisory

This security advisory describes one critical risk vulnerability.

1) Type Confusion

Severity: Critical

CVSSv3: 8.4 [CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:H/RL:O/RC:C] [PCI]

CVE-ID: CVE-2019-17026

CWE-ID: CWE-843 - Access of Resource Using Incompatible Type ('Type Confusion')

Exploit availability: Yes [Search exploit]


The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to a type confusion error with StoreElementHole and FallibleStoreElement when processing HTML content in IonMonkey JIT compiler. A remote attacker can create a specially crafted webpage, trick the victim into visiting it, trigger a type confusion error and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

Note, this vulnerability is being actively exploited in the wild.


Update to Firefox 72.0.1 or Firefox ESR 68.4.1.

Vulnerable software versions

Mozilla Firefox: 65.0, 65.0.1, 65.0.2, 66.0, 66.0.1, 66.0.2, 66.0.3, 66.0.4, 66.0.5, 67.0, 67.0.1, 67.0.2, 67.0.3, 67.0.4, 68.0, 68.0.1, 68.0.2, 69.0, 69.0.1, 69.0.2, 69.0.3, 70.0, 70.0.1, 71.0, 72.0

Firefox ESR: 60.0, 60.0.1, 60.0.2, 60.1.0, 60.2.0, 60.2.1, 60.2.2, 60.3.0, 60.4.0, 60.5.0, 60.5.1, 60.5.2, 60.6.0, 60.6.1, 60.6.2, 60.6.3, 60.7.0, 60.7.1, 60.7.2, 60.8.0, 60.9.0, 68.0, 68.0.1, 68.0.2, 68.1.0, 68.2.0, 68.3.0, 68.4.0

CPE External links

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

How the attacker can exploit this vulnerability?

The attacker would have to trick the victim to visit a specially crafted website.

Is there known malware, which exploits this vulnerability?

Yes. This vulnerability is being exploited in the wild.