Description
Characters from the "Canadian Syllabics" unicode block can be mixed with characters from other unicode blocks in the addressbar instead of being rendered as their raw "punycode" form, allowing for domain name spoofing attacks through character confusion. The current Unicode standard allows characters from "Aspirational Use Scripts" such as Canadian Syllabics to be mixed with Latin characters in the "moderately restrictive" IDN profile. We have changed Firefox behavior to match the upcoming Unicode version 10.0 which removes this category and treats them as "Limited Use Scripts.". This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mozilla | Firefox | unspecified – < 54 | 54 |
| Mozilla | Firefox ESR | unspecified – < 52.2 | 52.2 |
| Mozilla | Thunderbird | unspecified – < 52.2 | 52.2 |
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 | 52.2.0esr-1 | — |
| Debian 13 | firefox-esr | 52.2.0esr-1 | — |
| Debian 12 | firefox-esr | 52.2.0esr-1 | — |
| Debian 9 | firefox-esr | 52.2.0esr-1~deb9u1 | DSA-3881-1 |
| Debian 9 | icedove | 1:52.2.1-4~deb9u1 | DSA-3918-1 |
| Debian 8 | firefox-esr | 52.2.0esr-1~deb8u1 | DSA-3881-1 |
| Debian 8 | icedove | 1:52.2.1-4~deb8u1 | DSA-3918-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 7 | firefox-esr | 52.2.0esr-1~deb7u1 | DLA-991-1 |
| Debian 7 | icedove | 1:52.2.1-1~deb7u1 | DLA-1007-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | firefox | 54.0+build3-0ubuntu0.16.04.1 | USN-3315-1 |
| Ubuntu 16.04 LTS | thunderbird | 1:52.2.1+build1-0ubuntu0.16.04.1 | USN-3321-1 |
| Ubuntu 14.04 LTS | firefox | 54.0+build3-0ubuntu0.14.04.1 | USN-3315-1 |
| Ubuntu 14.04 LTS | thunderbird | 1:52.2.1+build1-0ubuntu0.14.04.1 | USN-3321-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 7 | firefox +1 | 52.2.0-1.el7_3 | RHSA-2017:1561, RHSA-2017:1440 |
| RHEL 6 | firefox +1 | 52.2.0-1.el6_9 | RHSA-2017:1561, RHSA-2017:1440 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP2 | MozillaFirefox | 52.2.0esr-108.3 | SUSE-SU-2017:1669-1 |
| SLES 12 SP2 | MozillaFirefox-branding-SLE | 52-31.1 | SUSE-SU-2017:1669-1 |
| SLES 12 SP1 | MozillaFirefox | 52.2.0esr-108.3 | SUSE-SU-2017:1669-1 |
| SLES 12 SP1 | MozillaFirefox-branding-SLE | 52-31.1 | SUSE-SU-2017:1669-1 |
| SLES 12 | MozillaFirefox | 52.2.0esr-108.3 | SUSE-SU-2017:1669-1 |
| SLES 12 | MozillaFirefox-branding-SLE | 52-31.1 | SUSE-SU-2017:1669-1 |
| SLES 11 SP4 | MozillaFirefox | 52.2.0esr-72.5.2 | SUSE-SU-2017:2235-1 |
| SLES 11 SP4 | MozillaFirefox-branding-SLED | 52-24.3.44 | SUSE-SU-2017:2235-1 |
| SLES 11 SP4 | firefox-gcc5 +1 | 5.3.1+r233831-7.1 | SUSE-SU-2017:2235-1 |
| SLES 11 SP4 | mozilla-nss | 3.29.5-47.3.2 | SUSE-SU-2017:2235-1 |
| SLES 11 SP3 | MozillaFirefox | 52.2.0esr-72.5.2 | SUSE-SU-2017:2235-1 |
| SLES 11 SP3 | MozillaFirefox-branding-SLED | 52-24.3.44 | SUSE-SU-2017:2235-1 |
| SLES 11 SP3 | firefox-gcc5 +1 | 5.3.1+r233831-7.1 | SUSE-SU-2017:2235-1 |
| SLES 11 SP3 | mozilla-nss | 3.29.5-47.3.2 | SUSE-SU-2017:2235-1 |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP2 | MozillaFirefox | 52.2.0esr-108.3 | SUSE-SU-2017:1669-1 |
| SLES for SAP 12 SP2 | MozillaFirefox-branding-SLE | 52-31.1 | SUSE-SU-2017:1669-1 |
| SLES for SAP 12 SP1 | MozillaFirefox | 52.2.0esr-108.3 | SUSE-SU-2017:1669-1 |
| SLES for SAP 12 SP1 | MozillaFirefox-branding-SLE | 52-31.1 | SUSE-SU-2017:1669-1 |
| SLES for SAP 12 | MozillaFirefox | 52.2.0esr-108.3 | SUSE-SU-2017:1669-1 |
| SLES for SAP 12 | MozillaFirefox-branding-SLE | 52-31.1 | SUSE-SU-2017:1669-1 |
| SLES for SAP 11 SP4 | MozillaFirefox | 52.2.0esr-72.5.2 | SUSE-SU-2017:2235-1 |
| SLES for SAP 11 SP4 | MozillaFirefox-branding-SLED | 52-24.3.44 | SUSE-SU-2017:2235-1 |
| SLES for SAP 11 SP4 | firefox-gcc5 +1 | 5.3.1+r233831-7.1 | SUSE-SU-2017:2235-1 |
| SLES for SAP 11 SP4 | mozilla-nss | 3.29.5-47.3.2 | SUSE-SU-2017:2235-1 |
| SUSE Package Hub 12 | MozillaThunderbird | 52.2-36.1 | openSUSE-SU-2017:1579-1 |
| SUSE OpenStack Cloud 6 | MozillaFirefox | 52.2.0esr-108.3 | SUSE-SU-2017:1669-1 |
| SUSE OpenStack Cloud 6 | MozillaFirefox-branding-SLE | 52-31.1 | SUSE-SU-2017:1669-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | MozillaFirefox | 52.2.0esr-72.5.2 | SUSE-SU-2017:2235-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | MozillaFirefox-branding-SLED | 52-24.3.44 | SUSE-SU-2017:2235-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | firefox-gcc5 +1 | 5.3.1+r233831-7.1 | SUSE-SU-2017:2235-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | mozilla-nss | 3.29.5-47.3.2 | SUSE-SU-2017:2235-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | MozillaThunderbird | 91.1.1-1.1 | openSUSE-SU-2024:10601-1 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 7 | firefox +1 | 52.2.0-1.0.1.el7_3 | ELSA-2017-1561, ELSA-2017-1440 |
Advisories 14
- RHSA-2017:1561 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2017:1440 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- USN-3315-1 firefox vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- USN-3321-1 thunderbird vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- DLA-991-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-3918-1 icedove - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-3881-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-1007-1 icedove - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2017:2235-1 Security update for MozillaFirefox, MozillaFirefox-branding-SLED, firefox-gcc5, mozilla-nss SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2017:1579-1 Security update for Mozilla Thunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2017:1669-1 Security update for MozillaFirefox, MozillaFirefox-branding-SLE SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10601-1 MozillaThunderbird-91.1.1-1.1 on GA media SUSE / openSUSE Security Updates · May 7, 2025
- ELSA-2017-1561 Important: thunderbird security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Jun 21, 2017
- ELSA-2017-1440 Critical: firefox security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Jun 14, 2017
References
- 99057 vdb-entry
- http://www.unicode.org/reports/tr31/tr31-26.html#Aspirational_Use_Scripts
- https://www.mozilla.org/security/advisories/mfsa2017-15/
- DSA-3918 vendor-advisory
- 1038689 vdb-entry
- https://bugzilla.mozilla.org/show_bug.cgi?id=1364283
- DSA-3881 vendor-advisory
- RHSA-2017:1440 vendor-advisory
- RHSA-2017:1561 vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2017-17/
- https://www.mozilla.org/security/advisories/mfsa2017-16/