CVE-2021-23977

Name: CVE-2021-23977
Creator: NVD / NIST
Published: 2021-02-26T03:15:14.213+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.3/10EPSS 0.87%

Last modified Jun 17, 2026

CVE-2021-23977 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. Firefox for Android suffered from a time-of-check-time-of-use vulnerability that allowed a malicious application to read sensitive data from application directories. Note: This issue is only affected Firefox for Android. EPSS estimates a 0.87% chance of exploitation in the next 30 days.

Description

Firefox for Android suffered from a time-of-check-time-of-use vulnerability that allowed a malicious application to read sensitive data from application directories. Note: This issue is only affected Firefox for Android. Other operating systems are unaffected. This vulnerability affects Firefox < 86.

Metrics

CVSS 3.1

5.3/10

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

EPSS Probability

0.87%

54.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-367

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 86.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1684761Issue 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=1684761Issue 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-2021-23977?

How severe is CVE-2021-23977?

CVE-2021-23977 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.87% probability of exploitation in the next 30 days.

How do I fix CVE-2021-23977?

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-2021-23977?

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

Scan your code now

Source: NVD / NIST