Improperly implemented security check for standard in Firefox ESR and Mozilla Firefox - CVE-2020-26961

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Main Vulnerability Database Vulnerabilities #VU48466

Improperly implemented security check for standard in Firefox ESR and Mozilla Firefox - CVE-2020-26961

Published: November 17, 2020


Vulnerability identifier: #VU48466
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2020-26961
CWE-ID: CWE-358
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to perform a DNS rebinding attack.

The vulnerability exists due to the way Firefox filters IPv4 mapped IP addresses. When DNS over HTTPS is in use, it intentionally filters RFC1918 and related IP ranges from the responses as these do not make sense coming from a DoH resolver. However when an IPv4 address was mapped through IPv6, these addresses were erroneously let through, leading to a potential DNS Rebinding attack.


Affected software

Firefox ESR
Mozilla Firefox
Gentoo Linux
Arch Linux
Red Hat Enterprise Linux Desktop
Red Hat Enterprise Linux for Power, big endian
Red Hat Enterprise Linux Server
Red Hat Enterprise Linux Workstation
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Scientific Computing
CentOS
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux Server - TUS
Ubuntu
openEuler
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
Red Hat Enterprise Linux Server for x86_64 - Update Services for SAP Solutions
thunderbird (Red Hat package)
firefox (Red Hat package)
firefox-esr (Debian package)
thunderbird (Debian package)
firefox (Alpine package)
firefox-esr (Alpine package)
thunderbird (Alpine package)
thunderbird (Ubuntu package)
firefox
firefox-debuginfo
firefox-debugsource
mozilla-crashreporter-firefox-debuginfo
firefox (Ubuntu package)
Mozilla Thunderbird
Firefox for Android

How to mitigate CVE-2020-26961

Install updates from vendor's website.

Firefox ESR - update to 78.5.0
Mozilla Firefox - update to 83.0
Mozilla Thunderbird - update to 78.5.0
thunderbird (Red Hat package) - addressed in versions 78.5.0-1.el6_10, 78.5.0-1.el7_9, 78.5.0-1.el8_0, 78.5.0-1.el8_1, 78.5.0-1.el8_2, 78.5.0-1.el8_3
firefox (Red Hat package) - addressed in versions 78.5.0-1.el6_10, 78.5.0-1.el7_9, 78.5.0-1.el8_0, 78.5.0-1.el8_1, 78.5.0-1.el8_2, 78.5.0-1.el8_3
firefox-esr (Debian package) - update to 78.5.0esr-1~deb10u1
thunderbird (Debian package) - update to 1:78.5.0-1~deb10u1
firefox-esr (Alpine package) - update to 78.5.0-r0
thunderbird (Alpine package) - update to 78.5.1-r0
Firefox for Android - update to 83.0.0
thunderbird (Ubuntu package) - update to 1:78.5.0+build3-0ubuntu0.20.10.1
firefox - update to 79.0-12
firefox-debuginfo - update to 79.0-12
firefox-debugsource - update to 79.0-12
mozilla-crashreporter-firefox-debuginfo - update to 79.0-12
firefox (Ubuntu package) - addressed in versions 83.0+build2-0ubuntu0.16.04.3, 83.0+build2-0ubuntu0.18.04.2, 83.0+build2-0ubuntu0.20.04.1, 83.0+build2-0ubuntu0.20.10.1

External References

Related Security Bulletins