CVE-2021-4221 Other in Firefox

Q: Is CVE-2021-4221 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-4221 exists.

Q: How do I fix CVE-2021-4221?

No fix has been published for CVE-2021-4221 yet. Limit exposure of the affected software until one is available.

Medium 4.3 Published 22 Dec 2022 Updated 16 Apr 2025

RTL characters in domain names caused visual spoofing on Firefox for Android, enabling user confusion and potential phishing attacks.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2021-4221?

CVE-2021-4221 is a medium-severity vulnerability in Mozilla Firefox, published on 22 Dec 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official 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.

Weakness: CWE-1007

Which versions are affected by CVE-2021-4221?

It affects 1 product.

Products include Mozilla Firefox.

How do I fix CVE-2021-4221?

No fix has been published for CVE-2021-4221 yet. Limit exposure of the affected software until one is available.

Is CVE-2021-4221 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-4221 exists.

All Mozilla Firefox vulnerabilities

Sources

Also known as GHSA-wmph-fgw4-55rj.