CVE-2026-100831
Received Received - Intake

Use-after-free in Firefox ESR and Firefox

Publication date: 2026-09-29

Last updated on: 2026-09-29

Assigner: Mozilla Corporation

Description
Use-after-free in the DOM: UI Events & Focus Handling component. This vulnerability was fixed in Firefox ESR 153.4 and Firefox 157.

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Meta Information

Published
2026-09-29
Last Modified
2026-09-29
Generated
2026-09-29
AI Q&A
2026-09-29
EPSS Evaluated
N/A
NVD
CVE-2026-100831
EUVD
EUVD-2026-88809

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
mozilla firefox to 153.4 (inc)
mozilla firefox to 157 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-416 The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

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Executive Summary

This is a use-after-free vulnerability in Firefox's DOM UI Events & Focus Handling component. It allows an attacker to access memory after it has been freed, potentially leading to code execution or crashes.

Detection Guidance

Detection requires checking Firefox version. Run 'firefox --version' to verify if it is below Firefox ESR 153.4 or Firefox 157. If so, the system is vulnerable.

Impact Analysis

An attacker could exploit this to execute arbitrary code, crash the browser, or gain control of your system. It requires user interaction to trigger, such as visiting a malicious website.

Mitigation Strategies

Update Firefox to ESR 153.4 or Firefox 157 or later immediately. Disable automatic updates if not already enabled to prevent exposure.

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