CVE-2021-38493 Memory corruption in Firefox

Q: Is CVE-2021-38493 being exploited?

There is no known exploitation of CVE-2021-38493 in the wild and no public exploit code.

High 8.8 Published 3 Nov 2021 Updated 4 Aug 2024

Memory safety bugs in Firefox and Thunderbird allow attackers to execute arbitrary code via crafted web content.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2021-38493?

CVE-2021-38493 is a high-severity memory corruption vulnerability in Mozilla Firefox, published on 3 Nov 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Mozilla developers reported memory safety bugs present in Firefox 91 and Firefox ESR 78.13. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 78.14, Thunderbird < 78.14, and Firefox < 92.

Weakness: CWE-787

Which versions are affected by CVE-2021-38493?

It affects 3 products.

Linux distribution packages (32)

`firefox` Red Hat:enterprise_linux:7::client	All versions	`0:78.14.0-1.el7_9`
`firefox-debuginfo` Red Hat:enterprise_linux:7::client	All versions	`0:78.14.0-1.el7_9`
`thunderbird` Red Hat:enterprise_linux:7::client	All versions	`0:78.14.0-1.el7_9`
`thunderbird-debuginfo` Red Hat:enterprise_linux:7::client	All versions	`0:78.14.0-1.el7_9`
`firefox` Red Hat:enterprise_linux:7::server	All versions	`0:78.14.0-1.el7_9`
`firefox-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:78.14.0-1.el7_9`
`thunderbird` Red Hat:enterprise_linux:7::server	All versions	`0:78.14.0-1.el7_9`
`thunderbird-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:78.14.0-1.el7_9`
`firefox` Red Hat:enterprise_linux:7::workstation	All versions	`0:78.14.0-1.el7_9`
`firefox-debuginfo` Red Hat:enterprise_linux:7::workstation	All versions	`0:78.14.0-1.el7_9`
`thunderbird` Red Hat:enterprise_linux:7::workstation	All versions	`0:78.14.0-1.el7_9`
`thunderbird-debuginfo` Red Hat:enterprise_linux:7::workstation	All versions	`0:78.14.0-1.el7_9`
`firefox` Red Hat:enterprise_linux:8::appstream	All versions	`0:78.14.0-1.el8_4`
`firefox-debuginfo` Red Hat:enterprise_linux:8::appstream	All versions	`0:78.14.0-1.el8_4`
`firefox-debugsource` Red Hat:enterprise_linux:8::appstream	All versions	`0:78.14.0-1.el8_4`
`thunderbird` Red Hat:enterprise_linux:8::appstream	All versions	`0:78.14.0-1.el8_4`
`thunderbird-debuginfo` Red Hat:enterprise_linux:8::appstream	All versions	`0:78.14.0-1.el8_4`
`thunderbird-debugsource` Red Hat:enterprise_linux:8::appstream	All versions	`0:78.14.0-1.el8_4`
`firefox` Red Hat:rhel_eus:8.1::appstream	All versions	`0:78.14.0-1.el8_1`
`firefox-debuginfo` Red Hat:rhel_eus:8.1::appstream	All versions	`0:78.14.0-1.el8_1`
`firefox-debugsource` Red Hat:rhel_eus:8.1::appstream	All versions	`0:78.14.0-1.el8_1`
`thunderbird` Red Hat:rhel_eus:8.1::appstream	All versions	`0:78.14.0-1.el8_1`
`thunderbird-debuginfo` Red Hat:rhel_eus:8.1::appstream	All versions	`0:78.14.0-1.el8_1`
`thunderbird-debugsource` Red Hat:rhel_eus:8.1::appstream	All versions	`0:78.14.0-1.el8_1`
`firefox` Red Hat:rhel_eus:8.2::appstream	All versions	`0:78.14.0-1.el8_2`
`firefox-debuginfo` Red Hat:rhel_eus:8.2::appstream	All versions	`0:78.14.0-1.el8_2`
`firefox-debugsource` Red Hat:rhel_eus:8.2::appstream	All versions	`0:78.14.0-1.el8_2`
`thunderbird` Red Hat:rhel_eus:8.2::appstream	All versions	`0:78.14.0-1.el8_2`
`thunderbird-debuginfo` Red Hat:rhel_eus:8.2::appstream	All versions	`0:78.14.0-1.el8_2`
`thunderbird-debugsource` Red Hat:rhel_eus:8.2::appstream	All versions	`0:78.14.0-1.el8_2`
`firefox` Rocky Linux:8	All versions	`0:78.14.0-1.el8_4`
`thunderbird` Rocky Linux:8	All versions	`0:78.14.0-1.el8_4`

Products include Mozilla Firefox, Mozilla Firefox Esr, Mozilla Thunderbird.

How do I fix CVE-2021-38493?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2021-38493 being exploited?

There is no known exploitation of CVE-2021-38493 in the wild and no public exploit code.

All Mozilla Firefox vulnerabilities

Sources

Also known as DEBIAN-CVE-2021-38493, DLA-2756-1, DLA-2757-1, DSA-4969-1, DSA-4973-1, GHSA-6rrw-rx8w-qx97 and 14 more.