CVE-2021-4221

Name: CVE-2021-4221
Creator: NVD / NIST
Published: 2022-12-22T20:15:12.337+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 0.41%

Last modified Jun 17, 2026

CVE-2021-4221 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. 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. EPSS estimates a 0.41% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

4.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

EPSS Probability

0.41%

32.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-1007

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 92.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1704422Exploit, Issue Tracking, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-38/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1704422Exploit, Issue Tracking, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-38/Vendor Advisory

Timeline

Published: Dec 22, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-4221?

How severe is CVE-2021-4221?

CVE-2021-4221 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.41% probability of exploitation in the next 30 days.

How do I fix CVE-2021-4221?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-4221?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST