CVE-2021-23975Public exploit

Browser crash via unchecked memory-size pointer

Published Feb 26, 2021 · Updated Aug 3, 2024

Invalid pointer handling in Firefox before 86 allows local users to crash the browser by invoking Measure on the about:memory page. WebRender's memory-reporting path calls its size function directly on an unowned pointer instead of using the API method that rejects invalid pointers. Exploitation requires an interactive user to open the developer page and select Measure, and the documented consequence is a browser-process abort.

CVSS severity6.5
Medium
EPSS probability1.02%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Invalid pointer handling in Firefox before 86 allows local users to crash the browser by invoking Measure on the about:memory page. WebRender's memory-reporting path calls its size function directly on an unowned pointer instead of using the API method that rejects invalid pointers. Exploitation requires an interactive user to open the developer page and select Measure, and the documented consequence is a browser-process abort.

The record

CVE
CVE-2021-23975
Published
Feb 26, 2021
Updated
Aug 3, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-862
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 86

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=< 86

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-862Missing Authorization

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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