CVE-2026-100779

Analyzed Analyzed - Analysis Complete

Use-after-free in Firefox XSLT Component

Publication date: 2026-09-29

Last updated on: 2026-10-05

Assigner: Mozilla Corporation

Description

Use-after-free in the XSLT 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

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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-2026-100779

EUVD

EUVD-2026-88931

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 157.0.0 (exc)
mozilla	thunderbird	to 157.0 (exc)
mozilla	firefox	From 115.1.0 (inc) to 115.42.0 (exc)
mozilla	firefox	From 140.0 (inc) to 140.17.0 (exc)
mozilla	firefox	From 153.0 (inc) to 153.4.0 (exc)
mozilla	thunderbird	From 140.0 (inc) to 140.17.0 (exc)
mozilla	thunderbird	From 153.0 (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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.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 XSLT component of Firefox browsers. 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 relates to a use-after-free issue in the XSLT component. Detection primarily involves checking the installed Firefox version and comparing it against the patched versions (Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, Firefox ESR 140.17). Use commands like 'firefox --version' or check your package manager for updates.

Impact Analysis

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

Compliance Impact

The provided CVE data does not specify how this vulnerability impacts compliance with standards like GDPR or HIPAA. The description only mentions a use-after-free issue in the XSLT component of Firefox, fixed in certain versions.

Mitigation Strategies

Update Firefox ESR to version 153.4 or later, Firefox to version 157 or later, or Firefox ESR 115.42 or later, and Firefox ESR 140.17 or later to address the use-after-free vulnerability in the XSLT component.

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