CVE-2021-23976

Name: CVE-2021-23976
Creator: NVD / NIST
Published: 2021-02-26T02:15:13.463+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.1/10EPSS 1.10%

Last modified Jun 17, 2026

CVE-2021-23976 is a high-severity vulnerability rated 8.1/10 on the CVSS scale. When accepting a malicious intent from other installed apps, Firefox for Android accepted manifests from arbitrary file paths and allowed declaring webapp manifests for other origins. This could be used to gain fullscreen access for UI spoofing and could also lead to cross-origin attacks on targeted websites. EPSS estimates a 1.10% chance of exploitation in the next 30 days.

Description

When accepting a malicious intent from other installed apps, Firefox for Android accepted manifests from arbitrary file paths and allowed declaring webapp manifests for other origins. This could be used to gain fullscreen access for UI spoofing and could also lead to cross-origin attacks on targeted websites. Note: This issue is a different issue from CVE-2020-26954 and only affected Firefox for Android. Other operating systems are unaffected. This vulnerability affects Firefox < 86.

Metrics

CVSS 3.1

8.1/10

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

EPSS Probability

1.10%

61.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-1021

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 86.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1684627Issue Tracking, Permissions Required, Vendor Advisory
https://security.gentoo.org/glsa/202104-10Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2021-07/Release Notes, Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1684627Issue Tracking, Permissions Required, Vendor Advisory
https://security.gentoo.org/glsa/202104-10Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2021-07/Release Notes, Vendor Advisory

Timeline

Published: Feb 26, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-23976?

How severe is CVE-2021-23976?

CVE-2021-23976 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 1.10% probability of exploitation in the next 30 days.

How do I fix CVE-2021-23976?

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-2021-23976?

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

Scan your code now

Source: NVD / NIST