CVE-2026-100796

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Use-after-free in Firefox JavaScript WebAssembly

Publication date: 2026-09-29

Last updated on: 2026-09-30

Assigner: Mozilla Corporation

Description

Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Thunderbird 157 and Firefox 157.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-09-29

Last Modified

2026-09-30

Generated

2026-10-19

AI Q&A

2026-09-29

EPSS Evaluated

2026-10-18

NVD

CVE-2026-100796

EUVD

EUVD-2026-88949

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	157

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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.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 JavaScript WebAssembly component. Use-after-free means the software tries to use memory after it has been freed, which can lead to crashes or arbitrary code execution. It was fixed in Firefox version 157.

Detection Guidance

This vulnerability is specific to Firefox versions before 157. Detection involves checking Firefox version and monitoring for unusual JavaScript or WebAssembly activity. Use commands like 'firefox --version' to check the installed version. If version is below 157, the system is vulnerable.

Impact Analysis

An attacker could exploit this to crash your browser or run malicious code on your system. This might allow them to steal data, install malware, or take control of your device if you visit a specially crafted website.

Compliance Impact

The vulnerability is a use-after-free in Firefox's JavaScript: WebAssembly component, which could allow arbitrary code execution. This may impact compliance with GDPR by risking unauthorized data access or processing, and with HIPAA by potentially exposing protected health information if exploited.

Mitigation Strategies

Update Firefox to version 157 or later to address the use-after-free vulnerability in the JavaScript: WebAssembly component.

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