Permissions, Privileges, and Access Controls in Mozilla Firefox - CVE-2020-12391

Vulnerability identifier: #VU27534

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-2020-12391

CWE-ID: CWE-264

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to documents formed using data: URLs in an object element failed to inherit the CSP of the creating context. A remote attacker can execute arbitrary scripts that should have been blocked, albeit with a unique opaque origin.

Mozilla Firefox
Arch Linux
firefox (Ubuntu package)
firefox (Alpine package)

Install updates from vendor's website.

Mozilla Firefox - update to 76.0
firefox (Ubuntu package) - addressed in versions 76.0+build2-0ubuntu0.16.04.1, 76.0+build2-0ubuntu0.18.04.1, 76.0+build2-0ubuntu0.19.10.1, 76.0+build2-0ubuntu0.20.04.1, 76.0.1+build1-0ubuntu0.16.04.1, 76.0.1+build1-0ubuntu0.18.04.1, 76.0.1+build1-0ubuntu0.19.10.1, 76.0.1+build1-0ubuntu0.20.04.1
firefox (Alpine package) - update to 76.0-r0

• https://www.mozilla.org/en-US/security/advisories/mfsa2020-16/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1457100

• Multiple vulnerabilities in Mozilla Firefox and Firefox ESR
• Arch Linux update for firefox
• Ubuntu update for Firefox
• Ubuntu regressions update for Firefox
• Permissions, Privileges, and Access Controls in firefox (Alpine package)