CVE-2017-7764: Debian Linux

Medium severity, CVSS 5.3. EPSS: 2% chance of exploitation in the next 30 days.

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

• Debian Debian Linux: version 8.0 only; version 9.0 only
• Mozilla Firefox: before 52.2.0 (fixed in 52.2.0); before 54.0 (fixed in 54.0)
• Mozilla Thunderbird: before 52.2.0 (fixed in 52.2.0)

Published 2018-06-11. Last modified 2026-06-17.