MitM-attack in Mozilla Firefox ESR

Published: 2021-01-26
Risk Low
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2020-26976
Exploitation vector Network
Public exploit N/A
Vulnerable software
Firefox ESR
Client/Desktop applications / Web browsers

Vendor Mozilla

Security Bulletin

This security bulletin contains one low risk vulnerability.

1) Resource management error

EUVDB-ID: #VU49018

Risk: Low


CVE-ID: CVE-2020-26976

CWE-ID: CWE-399 - Resource Management Errors

Exploit availability: No


The vulnerability allows a remote attacker to gain access to sensitive information.

The vulnerability exists due to improper management of internal resources within the application, when processing embedded elements with https/http protocols. When a HTTPS pages was embedded in a HTTP page, and there was a service worker registered for the former, the service worker could have intercepted the request for the secure page despite the iframe not being a secure context due to the (insecure) framing.


Install update from vendor's website

Vulnerable software versions

Firefox ESR: 78.0 - 78.6.1, 68.0 - 68.12.0, 60.0 - 60.9.0

CPE2.3 External links

Q & A

Can this vulnerability be exploited remotely?

How the attacker can exploit this vulnerability?

Is there known malware, which exploits this vulnerability?