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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mozilla | Firefox ESR | unspecified – < 78.14 | 78.14 |
| Mozilla | Thunderbird | unspecified – < 78.14 | 78.14 |
| Mozilla | Firefox | unspecified – < 92 | 92 |
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 | 78.14.0esr-1 | — |
| Debian 14 | thunderbird | 1:78.14.0-1 | — |
| Debian 13 | firefox-esr | 78.14.0esr-1 | — |
| Debian 13 | thunderbird | 1:78.14.0-1 | — |
| Debian 12 | firefox-esr | 78.14.0esr-1 | — |
| Debian 12 | thunderbird | 1:78.14.0-1 | — |
| Debian 11 | firefox-esr | 78.14.0esr-1~deb11u1 | DSA-4969-1 |
| Debian 11 | thunderbird | 1:78.14.0-1~deb11u1 | DSA-4973-1 |
| Debian 10 | firefox-esr | 78.14.0esr-1~deb10u1 | DSA-4969-1 |
| Debian 10 | thunderbird | 1:78.14.0-1~deb10u1 | DSA-4973-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 9 | firefox-esr | 78.14.0esr-1~deb9u1 | DLA-2756-1 |
| Debian 9 | thunderbird | 1:78.14.0-1~deb9u1 | DLA-2757-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | mozjs78 | No fix yet | — |
| Ubuntu 20.04 LTS | firefox | 92.0+build3-0ubuntu0.20.04.1 | USN-5074-1 |
| Ubuntu 20.04 LTS | mozjs52 +1 | No fix yet | — |
| Ubuntu 20.04 LTS | thunderbird | 1:78.14.0+build1-0ubuntu0.20.04.1 | USN-5146-1 |
| Ubuntu 18.04 LTS | firefox | 92.0+build3-0ubuntu0.18.04.1 | USN-5074-1 |
| Ubuntu 18.04 LTS | mozjs38 +1 | No fix yet | — |
| Ubuntu 18.04 LTS | thunderbird | 1:78.14.0+build1-0ubuntu0.18.04.1 | USN-5146-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | firefox +1 | 78.14.0-1.el8_4 | RHSA-2021:3499, RHSA-2021:3497 |
| RHEL 7 | firefox +1 | 78.14.0-1.el7_9 | RHSA-2021:3498, RHSA-2021:3494 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.2 EUS | firefox +1 | 78.14.0-1.el8_2 | RHSA-2021:3500, RHSA-2021:3496 |
| RHEL 8.1 EUS | firefox +1 | 78.14.0-1.el8_1 | RHSA-2021:3501, RHSA-2021:3495 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | firefox +1 | 78.14.0-1.el8_4 | RLSA-2021:3499, RLSA-2021:3497 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP3 | MozillaThunderbird | 91.4.0-8.45.2 | SUSE-SU-2021:4150-1 |
| SLES 15 SP2 | MozillaThunderbird | 91.4.0-8.45.2 | SUSE-SU-2021:4150-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | MozillaFirefox | 92.0-1.2 | openSUSE-SU-2024:10600-1 |
| openSUSE Tumbleweed | firefox-esr | 128.5.1-1.1 | openSUSE-SU-2024:14572-1 |
| openSUSE Leap 15.3 | MozillaThunderbird | 91.4.0-8.45.2 | openSUSE-SU-2021:4150-1 |
| openSUSE Leap 15.2 | MozillaThunderbird | 91.4.0-lp152.2.52.1 | openSUSE-SU-2021:1635-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | librewolf | 92.0.1-r0 | — |
| Alpine v3.23 | firefox +1 | 92.0.1-r0 | — |
| Alpine v3.23 | firefox-esr | 91.2.0-r0 | — |
| Alpine v3.23 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.22 | firefox +1 | 92.0.1-r0 | — |
| Alpine v3.22 | firefox-esr | 91.2.0-r0 | — |
| Alpine v3.22 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.21 | firefox +1 | 92.0.1-r0 | — |
| Alpine v3.21 | firefox-esr | 91.2.0-r0 | — |
| Alpine v3.21 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.20 | firefox | 92.0.1-r0 | — |
| Alpine v3.20 | firefox-esr | 91.2.0-r0 | — |
| Alpine v3.20 | thunderbird | 91.3.2-r0 | — |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | firefox | 92.0.1-r0 | — |
| Alpine v3.19 | firefox-esr | 91.2.0-r0 | — |
| Alpine v3.19 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.18 | firefox | 92.0.1-r0 | — |
| Alpine v3.18 | firefox-esr | 91.2.0-r0 | — |
| Alpine v3.18 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.17 | firefox | 92.0.1-r0 | — |
| Alpine v3.17 | firefox-esr | 91.2.0-r0 | — |
| Alpine v3.17 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.16 | firefox | 92.0.1-r0 | — |
| Alpine v3.16 | firefox-esr | 91.2.0-r0 | — |
| Alpine v3.16 | mozjs78 | 78.14.0-r0 | — |
| Alpine v3.16 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.15 | firefox | 92.0.1-r0 | — |
| Alpine v3.15 | firefox-esr | 91.2.0-r0 | — |
| Alpine v3.15 | mozjs78 | 78.14.0-r0 | — |
| Alpine v3.14 | mozjs78 +1 | 78.14.0-r0 | — |
| Alpine v3.13 | mozjs78 +1 | 78.14.0-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | thunderbird | 78.14.0-1.amzn2.0.1 | ALAS2-2021-1720 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | firefox +1 | 78.14.0-1.0.1.el8_4 | ELSA-2021-3499, ELSA-2021-3497 |
| Oracle Linux 7 | firefox +1 | 78.14.0-1.0.1.el7_9 | ELSA-2021-3498, ELSA-2021-3494 |
Advisories 26
- RHSA-2021:3498 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2021:3494 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- USN-5146-1 thunderbird vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- USN-5074-1 firefox vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- DSA-4969-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-4973-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2757-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2756-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2021:3499 Important: thunderbird security update Rocky Linux Security Advisories · Feb 5, 2026
- RLSA-2021:3497 Important: firefox security update Rocky Linux Security Advisories · Feb 5, 2026
- SUSE-SU-2021:4150-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:4150-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:1635-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10600-1 MozillaFirefox-92.0-1.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:14572-1 firefox-esr-128.5.1-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- RHSA-2021:3501 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:3500 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:3499 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:3496 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:3497 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:3495 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- ALAS2-2021-1720 Important: thunderbird security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Nov 4, 2021
- ELSA-2021-3499 Important: thunderbird security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Sep 13, 2021
- ELSA-2021-3498 Important: firefox security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Sep 13, 2021
- ELSA-2021-3494 Important: thunderbird security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Sep 13, 2021
- ELSA-2021-3497 Important: firefox security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Sep 13, 2021
References
- https://www.mozilla.org/security/advisories/mfsa2021-38/
- https://www.mozilla.org/security/advisories/mfsa2021-42/
- https://www.mozilla.org/security/advisories/mfsa2021-39/
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=1723391%2C1724101%2C1724107
- GLSA-202202-03 vendor-advisory
- GLSA-202208-14 vendor-advisory