CVE-2021-4221

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2022-12-22 · updated 2026-06-17
Weakness: CWE-1007

Description

If a domain name contained a RTL character, it would cause the domain to be rendered to the right of the path. This could lead to user confusion and spoofing attacks. <br>*This bug only affects Firefox for Android. Other operating systems are unaffected.*<br>*Note*: Due to a clerical error this advisory was not included in the original announcement, and was added in Feburary 2022. This vulnerability affects Firefox < 92.

Affected products

Mozilla Firefox: before 92.0 — fixed in 92.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 92.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1704422
https://www.mozilla.org/security/advisories/mfsa2021-38/
https://bugzilla.mozilla.org/show_bug.cgi?id=1704422
https://www.mozilla.org/security/advisories/mfsa2021-38/

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