Description
Mozilla developers and community members Julian Hector, Randell Jesup, Gabriele Svelto, Tyson Smith, Christian Holler, and Masayuki Nakano reported memory safety bugs present in Firefox 94. 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 < 95, Firefox ESR < 91.4.0, and Thunderbird < 91.4.0.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mozilla | Firefox | unspecified – < 95 | 95 |
| Mozilla | Firefox ESR | unspecified – < 91.4.0 | 91.4.0 |
| Mozilla | Thunderbird | unspecified – < 91.4.0 | 91.4.0 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | firefox-esr | 91.4.0esr-1 | — |
| Debian 14 | thunderbird | 1:91.4.0-1 | — |
| Debian 13 | firefox-esr | 91.4.0esr-1 | — |
| Debian 13 | thunderbird | 1:91.4.0-1 | — |
| Debian 12 | firefox-esr | 91.4.0esr-1 | — |
| Debian 12 | thunderbird | 1:91.4.0-1 | — |
| Debian 11 | firefox-esr | 91.4.1esr-1~deb11u1 | DSA-5026-1 |
| Debian 11 | thunderbird | 1:91.4.1-1~deb11u1 | DSA-5034-1 |
| Debian 10 | thunderbird | 1:91.4.1-1~deb10u1 | DSA-5034-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | thunderbird | 1:91.5.0+build1-0ubuntu0.20.04.1 | USN-5248-1 |
| Ubuntu 18.04 LTS | thunderbird | 1:91.5.0+build1-0ubuntu0.18.04.1 | USN-5248-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | firefox | 91.4.0-1.el8_5 | RHSA-2021:5013 |
| RHEL 8 | thunderbird | 91.4.0-2.el8_5 | RHSA-2021:5045 |
| RHEL 7 | firefox | 91.4.0-1.el7_9 | RHSA-2021:5014 |
| RHEL 7 | thunderbird | 91.4.0-3.el7_9 | RHSA-2021:5046 |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.4 EUS | firefox | 91.4.0-1.el8_4 | RHSA-2021:5015 |
| RHEL 8.4 EUS | thunderbird | 91.4.0-2.el8_4 | RHSA-2021:5048 |
| RHEL 8.2 EUS | firefox | 91.4.0-1.el8_2 | RHSA-2021:5016 |
| RHEL 8.2 EUS | thunderbird | 91.4.0-2.el8_2 | RHSA-2021:5047 |
| RHEL 8.1 E4S | firefox | 91.4.0-1.el8_1 | RHSA-2021:5017 |
| RHEL 8.1 E4S | thunderbird | 91.4.0-2.el8_1 | RHSA-2021:5055 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | firefox | 91.4.0-1.el8_5 | RLSA-2021:5013 |
| Rocky Linux 8 | thunderbird | 91.4.0-2.el8_5 | RLSA-2021:5045 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.23 | thunderbird | 91.4.0-r0 | — |
| Alpine v3.22 | thunderbird | 91.4.0-r0 | — |
| Alpine v3.21 | thunderbird | 91.4.0-r0 | — |
| Alpine v3.20 | thunderbird | 91.4.0-r0 | — |
| Alpine v3.19 | thunderbird | 91.4.0-r0 | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.18 | thunderbird | 91.4.0-r0 | — |
| Alpine v3.17 | thunderbird | 91.4.0-r0 | — |
| Alpine v3.16 | thunderbird | 91.4.0-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | thunderbird | 102.7.1-1.amzn2.0.1 | ALAS2-2023-1951 |
Advisories 17
- RHSA-2021:5046 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2021:5014 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- USN-5248-1 thunderbird vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- DSA-5034-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-5026-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2021:5013 Important: firefox security update Rocky Linux Security Advisories · Feb 4, 2026
- RLSA-2021:5045 Important: thunderbird security update Rocky Linux Security Advisories · Feb 4, 2026
- RHSA-2021:5055 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:5048 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:5047 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:5045 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:5017 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:5015 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:5016 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:5013 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- WID-SEC-2023-0839 Xerox FreeFlow Print Server: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 6, 2025
- ALAS2-2023-1951 Important: thunderbird security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Jan 30, 2025