CVE-2021-23975

Name: CVE-2021-23975
Creator: NVD / NIST
Published: 2021-02-26T02:15:13.383+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.02%

Last modified Jun 17, 2026

CVE-2021-23975 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. The developer page about:memory has a Measure function for exploring what object types the browser has allocated and their sizes. When this function was invoked we incorrectly called the sizeof function, instead of using the API method that checks for invalid pointers. EPSS estimates a 1.02% chance of exploitation in the next 30 days.

Description

The developer page about:memory has a Measure function for exploring what object types the browser has allocated and their sizes. When this function was invoked we incorrectly called the sizeof function, instead of using the API method that checks for invalid pointers. This vulnerability affects Firefox < 86.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.02%

58.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-862

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 86.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1685145Issue 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=1685145Issue 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-2021-23975?

How severe is CVE-2021-23975?

CVE-2021-23975 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.02% probability of exploitation in the next 30 days.

How do I fix CVE-2021-23975?

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-2021-23975?

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

Scan your code now

Source: NVD / NIST