Description
The iframe sandbox rules were not correctly applied to XSLT stylesheets, allowing an iframe to bypass restrictions such as executing scripts or navigating the top-level frame. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mozilla | Firefox | unspecified – < 94 | 94 |
| Mozilla | Thunderbird | unspecified – < 91.3 | 91.3 |
| Mozilla | Firefox ESR | unspecified – < 91.3 | 91.3 |
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 | 91.3.0esr-1 | — |
| Debian 14 | thunderbird | 1:91.3.0-1 | — |
| Debian 13 | firefox-esr | 91.3.0esr-1 | — |
| Debian 13 | thunderbird | 1:91.3.0-1 | — |
| Debian 12 | firefox-esr | 91.3.0esr-1 | — |
| Debian 12 | thunderbird | 1:91.3.0-1 | — |
| 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 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 9 | firefox-esr | 91.4.1esr-1~deb9u1 | DLA-2863-1 |
| Debian 9 | thunderbird | 1:91.4.1-1~deb9u1 | DLA-2874-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | firefox | 94.0+build3-0ubuntu1 | — |
| Ubuntu 22.04 LTS | mozjs78 | No fix yet | — |
| Ubuntu 22.04 LTS | thunderbird | 1:91.3.1+build1-0ubuntu1 | — |
| Ubuntu 20.04 LTS | firefox | 94.0+build3-0ubuntu0.20.04.1 | USN-5131-1 |
| Ubuntu 20.04 LTS | mozjs52 +1 | No fix yet | — |
| Ubuntu 20.04 LTS | thunderbird | 1:91.5.0+build1-0ubuntu0.20.04.1 | USN-5248-1 |
| Ubuntu 18.04 LTS | firefox | 94.0+build3-0ubuntu0.18.04.1 | USN-5131-1 |
| Ubuntu 18.04 LTS | mozjs38 +1 | No fix yet | — |
| 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 | 91.3.0-1.el8_4 | RHSA-2021:4123 |
| RHEL 8 | thunderbird | 91.3.0-2.el8_4 | RHSA-2021:4130 |
| RHEL 7 | firefox | 91.3.0-1.el7_9 | RHSA-2021:4116 |
| RHEL 7 | thunderbird | 91.3.0-2.el7_9 | RHSA-2021:4134 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.2 EUS | firefox | 91.3.0-1.el8_2 | RHSA-2021:4605 |
| RHEL 8.2 EUS | thunderbird | 91.3.0-2.el8_2 | RHSA-2021:4132 |
| RHEL 8.1 EUS | firefox | 91.3.0-1.el8_1 | RHSA-2021:4607 |
| RHEL 8.1 EUS | thunderbird | 91.3.0-2.el8_1 | RHSA-2021:4133 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | firefox | 91.3.0-1.el8_4.alma | ALSA-2021:4123 |
| AlmaLinux 8 | thunderbird | 91.3.0-2.el8_4.alma | ALSA-2021:4130 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | firefox | 91.3.0-1.el8 | RLSA-2021:4123 |
| Rocky Linux 8 | thunderbird | 91.3.0-2.el8 | RLSA-2021:4130 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP3 | MozillaFirefox | 91.3.0-152.6.1 | SUSE-SU-2021:3745-1 |
| SLES 15 SP3 | MozillaThunderbird | 91.4.0-8.45.2 | SUSE-SU-2021:4150-1 |
| SLES 15 SP2 | MozillaFirefox | 91.3.0-152.6.1 | SUSE-SU-2021:3745-1 |
| SLES 15 SP2 | MozillaThunderbird | 91.4.0-8.45.2 | SUSE-SU-2021:4150-1 |
| SLES 15 SP1 | MozillaFirefox | 91.3.0-150.6.1 | SUSE-SU-2021:3651-1 |
| SLES 15 | MozillaFirefox | 91.3.0-150.6.1 | SUSE-SU-2021:3651-1 |
| SLES 12 SP5 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
Show 16 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP4 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SLES 12 SP3 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SLES 12 SP2 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SLES for SAP 15 SP1 | MozillaFirefox | 91.3.0-150.6.1 | SUSE-SU-2021:3651-1 |
| SLES for SAP 15 | MozillaFirefox | 91.3.0-150.6.1 | SUSE-SU-2021:3651-1 |
| SLES for SAP 12 SP5 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SLES for SAP 12 SP4 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SLES for SAP 12 SP3 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SLE HPC 15 SP1 | MozillaFirefox | 91.3.0-150.6.1 | SUSE-SU-2021:3651-1 |
| SLE HPC 15 | MozillaFirefox | 91.3.0-150.6.1 | SUSE-SU-2021:3651-1 |
| SUSE OpenStack Cloud Crowbar 9 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SUSE OpenStack Cloud Crowbar 8 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SUSE OpenStack Cloud 9 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SUSE OpenStack Cloud 8 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SUSE HPE Helion OpenStack 8 | MozillaFirefox | 91.3.0-112.80.2 | SUSE-SU-2021:3721-1 |
| SUSE Enterprise Storage 6 | MozillaFirefox | 91.3.0-150.6.1 | SUSE-SU-2021:3651-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | MozillaFirefox | 94.0.1-1.1 | openSUSE-SU-2024:11614-1 |
| openSUSE Tumbleweed | MozillaThunderbird | 91.3.0-1.1 | openSUSE-SU-2024:11607-1 |
| openSUSE Tumbleweed | firefox-esr | 128.5.1-1.1 | openSUSE-SU-2024:14572-1 |
| openSUSE Leap 15.3 | MozillaFirefox | 91.3.0-152.6.1 | openSUSE-SU-2021:3745-1 |
| 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 | 94.0-r0 | — |
| Alpine v3.23 | firefox +1 | 94.0-r0 | — |
| Alpine v3.23 | firefox-esr | 91.3.0-r0 | — |
| Alpine v3.23 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.22 | firefox +1 | 94.0-r0 | — |
| Alpine v3.22 | firefox-esr | 91.3.0-r0 | — |
| Alpine v3.22 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.21 | firefox +1 | 94.0-r0 | — |
| Alpine v3.21 | firefox-esr | 91.3.0-r0 | — |
| Alpine v3.21 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.20 | firefox | 94.0-r0 | — |
| Alpine v3.20 | firefox-esr | 91.3.0-r0 | — |
| Alpine v3.20 | thunderbird | 91.3.2-r0 | — |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | firefox | 94.0-r0 | — |
| Alpine v3.19 | firefox-esr | 91.3.0-r0 | — |
| Alpine v3.19 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.18 | firefox | 94.0-r0 | — |
| Alpine v3.18 | firefox-esr | 91.3.0-r0 | — |
| Alpine v3.18 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.17 | firefox | 94.0-r0 | — |
| Alpine v3.17 | firefox-esr | 91.3.0-r0 | — |
| Alpine v3.17 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.16 | firefox | 94.0-r0 | — |
| Alpine v3.16 | firefox-esr | 91.3.0-r0 | — |
| Alpine v3.16 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.15 | firefox | 94.0-r0 | — |
| Alpine v3.15 | firefox-esr | 91.3.0-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | thunderbird | 91.6.0-1.amzn2.0.1 | ALAS2-2022-1818 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | firefox | 91.3.0-1.0.1.el8_4 | ELSA-2021-4123 |
| Oracle Linux 8 | thunderbird | 91.3.0-2.0.1.el8_4 | ELSA-2021-4130 |
| Oracle Linux 7 | firefox | 91.3.0-1.0.1.el7_9 | ELSA-2021-4116 |
| Oracle Linux 7 | thunderbird | 91.3.0-2.0.1.el7_9 | ELSA-2021-4134 |
Advisories 34
- ALSA-2021:4123 Important: firefox security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2021:4130 Important: thunderbird security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2021:4134 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2021:4116 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
- USN-5131-1 firefox vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 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
- DLA-2863-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2874-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2021:4123 Important: firefox security update Rocky Linux Security Advisories · Feb 4, 2026
- RLSA-2021:4130 Important: thunderbird security update Rocky Linux Security Advisories · Feb 4, 2026
- SUSE-SU-2021:4150-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:3651-1 Security update for MozillaFirefox 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-2024:11607-1 MozillaThunderbird-91.3.0-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:1635-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:3721-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:3745-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:3745-1 Security update for MozillaFirefox 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-2021:4607 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:4605 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:4133 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:4132 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:4123 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:4130 Red Hat Security Advisory: thunderbird 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
- openSUSE-SU-2024:11614-1 MozillaFirefox-94.0.1-1.1 on GA media SUSE / openSUSE Security Updates · May 7, 2025
- ALAS2-2022-1818 Important: thunderbird security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Aug 21, 2022
- ELSA-2021-4134 Important: thunderbird security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Nov 5, 2021
- ELSA-2021-4130 Important: thunderbird security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 5, 2021
- ELSA-2021-4123 Important: firefox security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 4, 2021
- ELSA-2021-4116 Important: firefox security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Nov 4, 2021
References
- https://www.mozilla.org/security/advisories/mfsa2021-49/
- https://www.mozilla.org/security/advisories/mfsa2021-50/
- https://www.mozilla.org/security/advisories/mfsa2021-48/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1729517
- DSA-5026 vendor-advisory
- [debian-lts-announce] 20211229 [SECURITY] [DLA 2863-1] firefox-esr security update mailing-list
- DSA-5034 vendor-advisory
- [debian-lts-announce] 20220104 [SECURITY] [DLA 2874-1] thunderbird security update mailing-list
- GLSA-202202-03 vendor-advisory
- GLSA-202208-14 vendor-advisory