CVE-2026-100776

Analyzed Analyzed - Analysis Complete

Use-after-free in Firefox JavaScript WebAssembly

Publication date: 2026-09-29

Last updated on: 2026-10-06

Assigner: Mozilla Corporation

Description

Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, and Firefox ESR 140.17.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-09-29

Last Modified

2026-10-06

Generated

2026-10-19

AI Q&A

2026-09-29

EPSS Evaluated

2026-10-18

NVD

CVE-2026-100776

EUVD

EUVD-2026-88928

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	thunderbird	From 140.0 (inc) to 140.17.0 (exc)
mozilla	thunderbird	From 153.0 (inc) to 153.4.0 (exc)
mozilla	firefox	From 140.0.0 (inc) to 140.17.0 (exc)
mozilla	firefox	From 153.0.0 (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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.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 the JavaScript WebAssembly component of Firefox. Use-after-free 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 can be detected by checking the installed version. If you are running Firefox ESR 153.4 or earlier, Firefox 157 or earlier, or Firefox ESR 140.17 or earlier, your system is vulnerable. Update to the patched versions immediately.

Impact Analysis

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

Compliance Impact

The provided CVE data does not specify direct impacts on compliance with GDPR, HIPAA, or other standards. The vulnerability involves a use-after-free in JavaScript: WebAssembly, which could lead to arbitrary code execution or memory corruption. Such issues may risk data integrity and confidentiality, potentially affecting compliance if exploited. However, no explicit details are provided.

Mitigation Strategies

Update Firefox ESR to version 153.4 or later and Firefox to version 157 or later to address the use-after-free vulnerability in the JavaScript: WebAssembly component.

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