What’s Vulnerable › Vulnerabilities

CVE-2017-7764

• Severity: medium (CVSS 5.3 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.0% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2018-06-11 · updated 2026-06-17
• Weakness: CWE-20

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

• Debian Linux: 8.0, 9.0
• Mozilla Firefox: before 52.2.0; before 54.0 — fixed in 52.2.0, 54.0
• Mozilla Thunderbird: before 52.2.0 — fixed in 52.2.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 52.2.0, 54.0; Mozilla Thunderbird 52.2.0. Check the vendor advisory for mitigations.

References

• http://www.securityfocus.com/bid/99057
• http://www.securitytracker.com/id/1038689
• http://www.unicode.org/reports/tr31/tr31-26.html#Aspirational_Use_Scripts
• https://access.redhat.com/errata/RHSA-2017:1440
• https://access.redhat.com/errata/RHSA-2017:1561
• https://bugzilla.mozilla.org/show_bug.cgi?id=1364283
• https://www.debian.org/security/2017/dsa-3881
• https://www.debian.org/security/2017/dsa-3918
• https://www.mozilla.org/security/advisories/mfsa2017-15/
• https://www.mozilla.org/security/advisories/mfsa2017-16/
• https://www.mozilla.org/security/advisories/mfsa2017-17/
• http://www.securityfocus.com/bid/99057

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