CVE-2017-7764
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.
Does this matter?
Lower severity and a low EPSS score (1.96%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.0
- 5.3 MEDIUMCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- EPSS
- 1.96% probability · 80th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-20
- Affected
- mozilla/firefox · mozilla/thunderbird · debian/debian linux
- Source
- security@mozilla.org
EPSS 2.0% since 27 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://www.securityfocus.com/bid/99057Third Party Advisory, VDB Entry
- http://www.securitytracker.com/id/1038689Third Party Advisory, VDB Entry
- http://www.unicode.org/reports/tr31/tr31-26.html#Aspirational_Use_ScriptsThird Party Advisory
- https://access.redhat.com/errata/RHSA-2017:1440Third Party Advisory
- https://access.redhat.com/errata/RHSA-2017:1561Third Party Advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=1364283Exploit, Issue Tracking, Vendor Advisory
- https://www.debian.org/security/2017/dsa-3881Third Party Advisory
- https://www.debian.org/security/2017/dsa-3918Third Party Advisory
- https://www.mozilla.org/security/advisories/mfsa2017-15/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2017-16/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2017-17/Vendor Advisory
- http://www.securityfocus.com/bid/99057Third Party Advisory, VDB Entry
- http://www.securitytracker.com/id/1038689Third Party Advisory, VDB Entry
- http://www.unicode.org/reports/tr31/tr31-26.html#Aspirational_Use_ScriptsThird Party Advisory
- https://access.redhat.com/errata/RHSA-2017:1440Third Party Advisory
- https://access.redhat.com/errata/RHSA-2017:1561Third Party Advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=1364283Exploit, Issue Tracking, Vendor Advisory
- https://www.debian.org/security/2017/dsa-3881Third Party Advisory
- https://www.debian.org/security/2017/dsa-3918Third Party Advisory
- https://www.mozilla.org/security/advisories/mfsa2017-15/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2017-16/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2017-17/Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.