CVE-2021-23997

Name: CVE-2021-23997
Creator: NVD / NIST
Published: 2021-06-24T14:15:09.417+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 0.82%

Last modified Jun 17, 2026

CVE-2021-23997 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. Due to unexpected data type conversions, a use-after-free could have occurred when interacting with the font cache. We presume that with enough effort this could have been exploited to run arbitrary code. EPSS estimates a 0.82% chance of exploitation in the next 30 days.

Description

Due to unexpected data type conversions, a use-after-free could have occurred when interacting with the font cache. We presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox < 88.

Metrics

CVSS 3.1

8.8/10

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

EPSS Probability

0.82%

52.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-681

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 88.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1701942Issue Tracking, Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-16/Release Notes, Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1701942Issue Tracking, Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-16/Release Notes, Vendor Advisory

Timeline

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

Frequently Asked Questions

What is CVE-2021-23997?

How severe is CVE-2021-23997?

CVE-2021-23997 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.82% probability of exploitation in the next 30 days.

How do I fix CVE-2021-23997?

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-2021-23997?

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

Scan your code now

Source: NVD / NIST