Use-after-free in Firefox ESR - CVE-2021-43535
Published: November 2, 2021 / Updated: December 20, 2021
Vulnerability identifier: #VU57889
CSH Severity: High
CVSS v4: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2021-43535
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to compromise vulnerable system.
The vulnerability exists due to a use-after-free error when processing HTTP/2 session object. A remote attacker can trick the victim to open a specially crafted website, trigger a use-after-free error and execute arbitrary code on the system.
Successful exploitation of the vulnerability may allow an attacker to compromise vulnerable system.
Affected software
Firefox ESR
Ubuntu
firefox-esr (Debian package)
thunderbird (Debian package)
thunderbird (Ubuntu package)
Ubuntu
firefox-esr (Debian package)
thunderbird (Debian package)
thunderbird (Ubuntu package)
How to mitigate CVE-2021-43535
Install updates from vendor's website.
Firefox ESR - update to 91.3.0
firefox-esr (Debian package) - update to 91.4.1esr-1~deb11u1
thunderbird (Debian package) - addressed in versions 1:91.4.1-1~deb10u1, 1:91.4.1-1~deb11u1
thunderbird (Ubuntu package) - addressed in versions 1:91.5.0+build1-0ubuntu0.18.04.1, 1:91.5.0+build1-0ubuntu0.20.04.1
firefox-esr (Debian package) - update to 91.4.1esr-1~deb11u1
thunderbird (Debian package) - addressed in versions 1:91.4.1-1~deb10u1, 1:91.4.1-1~deb11u1
thunderbird (Ubuntu package) - addressed in versions 1:91.5.0+build1-0ubuntu0.18.04.1, 1:91.5.0+build1-0ubuntu0.20.04.1