CVE-2021-29953

Name: CVE-2021-29953
Creator: NVD / NIST
Published: 2021-06-24T14:15:10+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.1/10EPSS 0.65%

Last modified Jun 17, 2026

CVE-2021-29953 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. A malicious webpage could have forced a Firefox for Android user into executing attacker-controlled JavaScript in the context of another domain, resulting in a Universal Cross-Site Scripting vulnerability. *Note: This issue only affected Firefox for Android. EPSS estimates a 0.65% chance of exploitation in the next 30 days.

Description

A malicious webpage could have forced a Firefox for Android user into executing attacker-controlled JavaScript in the context of another domain, resulting in a Universal Cross-Site Scripting vulnerability. *Note: This issue only affected Firefox for Android. Other operating systems are unaffected. Further details are being temporarily withheld to allow users an opportunity to update.*. This vulnerability affects Firefox < 88.0.1 and Firefox for Android < 88.1.3.

Metrics

CVSS 3.1

6.1/10

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

EPSS Probability

0.65%

46.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 88.0.1
Mozilla	Firefox	< 88.1.3

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1701684Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-20/Release Notes, Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1701684Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-20/Release Notes, Vendor Advisory

Timeline

Published: Jun 24, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-29953?

How severe is CVE-2021-29953?

CVE-2021-29953 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 0.65% probability of exploitation in the next 30 days.

How do I fix CVE-2021-29953?

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-2021-29953?

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

Scan your code now

Source: NVD / NIST