CVE-2021-29971

Name: CVE-2021-29971
Creator: NVD / NIST
Published: 2021-08-05T20:15:08.58+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.02%

Last modified Jun 17, 2026

CVE-2021-29971 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. If a user had granted a permission to a webpage and saved that grant, any webpage running on the same host - irrespective of scheme or port - would be granted that permission. *This bug only affects Firefox for Android. EPSS estimates a 1.02% chance of exploitation in the next 30 days.

Description

If a user had granted a permission to a webpage and saved that grant, any webpage running on the same host - irrespective of scheme or port - would be granted that permission. *This bug only affects Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects Firefox < 90.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

1.02%

59.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-281

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 90.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1713638Issue Tracking, Permissions Required
https://www.mozilla.org/security/advisories/mfsa2021-28/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1713638Issue Tracking, Permissions Required
https://www.mozilla.org/security/advisories/mfsa2021-28/Vendor Advisory

Timeline

Published: Aug 5, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-29971?

How severe is CVE-2021-29971?

CVE-2021-29971 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.02% probability of exploitation in the next 30 days.

How do I fix CVE-2021-29971?

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-2021-29971?

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

Scan your code now

Source: NVD / NIST