CVE-2026-100785

Analyzed Analyzed - Analysis Complete

Use-after-Free in Mozilla Firefox ESR and Firefox

Publication date: 2026-09-29

Last updated on: 2026-10-05

Assigner: Mozilla Corporation

Description

Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-09-29

Last Modified

2026-10-05

Generated

2026-10-19

AI Q&A

2026-09-29

EPSS Evaluated

2026-10-18

NVD

CVE-2026-100785

EUVD

EUVD-2026-88937

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	From 154.0.0 (inc) to 157.0.0 (exc)
mozilla	thunderbird	From 154.0 (inc) to 157.0 (exc)
mozilla	firefox	to 115.42.0 (exc)
mozilla	firefox	From 116.0 (inc) to 140.17.0 (exc)
mozilla	firefox	From 141.0 (inc) to 153.4.0 (exc)
mozilla	thunderbird	to 140.17.0 (exc)
mozilla	thunderbird	From 141.0 (inc) to 153.4.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Attack-Flow Graph

Executive Summary

This is a use-after-free vulnerability in Firefox's DOM: Core & HTML component. It occurs when a program continues to use memory after it has been freed, potentially leading to crashes or arbitrary code execution.

Detection Guidance

This vulnerability is specific to Firefox browsers and was patched in newer versions. To detect it, check your Firefox version against the fixed releases (Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, Firefox ESR 140.17). Use commands like 'firefox --version' or check 'about:support' in Firefox.

Impact Analysis

An attacker could exploit this to crash your browser or run malicious code on your system. This may allow them to steal data, install malware, or take control of your device.

Compliance Impact

This vulnerability is a use-after-free in the DOM: Core & HTML component of Firefox, which could allow arbitrary code execution. Such vulnerabilities may lead to unauthorized data access or modification, potentially violating GDPR's data protection requirements or HIPAA's safeguards for protected health information.

Mitigation Strategies

Update Firefox to a patched version: Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, or Firefox ESR 140.17 or later. Remove or disable affected versions if updates are not immediately possible.

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