Cross-site scripting in Mozilla Firefox - CVE-2021-23974
Published: February 23, 2021
Vulnerability identifier: #VU50882
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N]
CVE-ID: CVE-2021-23974
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.
The vulnerability exists due to insufficient sanitization of user-supplied data. The DOMParser API did not properly process <noscript> elements for escaping. A remote attacker can bypass HTML Sanitizer and perform XSS attacks.
Affected software
Mozilla Firefox
Gentoo Linux
Ubuntu
firefox (Ubuntu package)
Gentoo Linux
Ubuntu
firefox (Ubuntu package)
How to mitigate CVE-2021-23974
Install updates from vendor's website.
Mozilla Firefox - update to 86.0
firefox (Ubuntu package) - addressed in versions 86.0+build3-0ubuntu0.16.04.1, 86.0+build3-0ubuntu0.18.04.1, 86.0+build3-0ubuntu0.20.04.1, 86.0+build3-0ubuntu0.20.10.1
firefox (Ubuntu package) - addressed in versions 86.0+build3-0ubuntu0.16.04.1, 86.0+build3-0ubuntu0.18.04.1, 86.0+build3-0ubuntu0.20.04.1, 86.0+build3-0ubuntu0.20.10.1