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Fencer Intel
medium 5.3

CVE-2017-7764 json

Characters from the "Canadian Syllabics" unicode block can be mixed with characters from other unicode blocks in the addressbar instead of…

published 2018-06-11 8 y ago modified 2026-06-17 4 mo ago also EUVD-2017-16739

cvss
5.3
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.0%
EPSS 2.0% chance of exploitation in 30 days, percentile 80%
public exploits
0
none known

Summary

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.

Patch / fix

  • Mozilla Firefox 54
  • Mozilla Firefox ESR 52.2
  • Mozilla Thunderbird 52.2
  • firefox-esr Debian 14, Debian 13, Debian 12 52.2.0esr-1

debian advisories DEBIAN-CVE-2017-7764

  • firefox Ubuntu 14.04 LTS 54.0+build3-0ubuntu0.14.04.1
  • firefox Ubuntu 16.04 LTS 54.0+build3-0ubuntu0.16.04.1
  • thunderbird Ubuntu 14.04 LTS 1:52.2.1+build1-0ubuntu0.14.04.1
  • thunderbird Ubuntu 16.04 LTS 1:52.2.1+build1-0ubuntu0.16.04.1

ubuntu advisories UBUNTU-CVE-2017-7764

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • thunderbird RHEL 6 52.2.0-1.el6_9
  • thunderbird RHEL 7 52.2.0-1.el7_3
  • firefox RHEL 6 52.2.0-1.el6_9
  • firefox RHEL 7 52.2.0-1.el7_3

red hat advisories RHSA-2017:1561RHSA-2017:1440

  • mozilla-nss SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +3 more 3.29.5-47.3.2
  • firefox-gcc5 SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +2 more 5.3.1+r233831-7.1
  • MozillaFirefox SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +3 more 52.2.0esr-72.5.2
  • firefox-libffi-gcc5 SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +2 more 5.3.1+r233831-7.1
  • MozillaFirefox-branding-SLED SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +2 more 52-24.3.44
  • MozillaFirefox-branding-SLE SLES for SAP 12 SP2, SLES for SAP 12 SP1, SLES for SAP 12 +6 more 52-31.1
  • MozillaFirefox SLES for SAP 12 SP2, SLES for SAP 12 SP1, SLES for SAP 12 +7 more 52.2.0esr-108.3

suse advisories SUSE-SU-2017:2235-1SUSE-SU-2017:1669-1

  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • MozillaThunderbird Package Hub 12 52.2-36.1

opensuse advisories openSUSE-SU-2024:10601-1openSUSE-SU-2017:1579-1

  • firefox Arch Linux 54.0-1
  • thunderbird Arch Linux 52.2.0-1

arch linux advisories AVG-302AVG-303

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2017-7764 updated cvss 5.3

Mozilla: Domain spoofing with combination of Canadian Syllabics and other unicode blocks (MFSA 2017-16)

  • Red Hat Enterprise Linux Client (v. 7) firefox 52.2.0-1.el7_3, thunderbird 52.2.0-1.el7_3 Red Hat Enterprise Linux Client Optional (v. 7) firefox 52.2.0-1.el7_3 Red Hat Enterprise Linux Desktop (v. 6) firefox 52.2.0-1.el6_9, thunderbird 52.2.0-1.el6_9 Red Hat Enterprise Linux Desktop Optional (v. 6) firefox 52.2.0-1.el6_9 Red Hat Enterprise Linux HPC Node Optional (v. 6) firefox 52.2.0-1.el6_9 Red Hat Enterprise Linux Server (v. 6) firefox 52.2.0-1.el6_9
    +7 more products
    Red Hat Enterprise Linux Server (v. 7) firefox 52.2.0-1.el7_3 Red Hat Enterprise Linux Server Optional (v. 6) firefox 52.2.0-1.el6_9, thunderbird 52.2.0-1.el6_9 Red Hat Enterprise Linux Server Optional (v. 7) firefox 52.2.0-1.el7_3, thunderbird 52.2.0-1.el7_3 Red Hat Enterprise Linux Workstation (v. 6) firefox 52.2.0-1.el6_9, thunderbird 52.2.0-1.el6_9 Red Hat Enterprise Linux Workstation (v. 7) firefox 52.2.0-1.el7_3, thunderbird 52.2.0-1.el7_3 Red Hat Enterprise Linux Workstation Optional (v. 6) firefox 52.2.0-1.el6_9 Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 52.2.0-1.el7_3
    fixed: vendor fix RHSA-2017:1440

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.96% chance of exploitation in the next 30 days, higher than 80% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • bugzilla.mozilla.org https://bugzilla.mozilla.org/show_bug.cgi?id=1364283 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.0 5.3 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N

Affected products

  • Mozilla Firefox
  • Mozilla Firefox ESR
  • Mozilla Thunderbird

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.