CVE-2026-100767

Analyzed Analyzed - Analysis Complete

Use-after-free in Firefox Networking Cache

Publication date: 2026-09-29

Last updated on: 2026-10-06

Assigner: Mozilla Corporation

Description

Use-after-free in the Networking: Cache 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:
Percentile:

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-2026-100767

EUVD

EUVD-2026-88919

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 153.0.0 (inc) to 153.4.0 (exc)
mozilla	firefox	From 115.0 (inc) to 115.42.0 (exc)
mozilla	firefox	From 140.0 (inc) to 140.17.0 (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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.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 Networking Cache component. 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 Mozilla Firefox and related ESR versions. Detection primarily involves checking installed Firefox versions against the patched releases. Use commands like 'firefox --version' to check your version. If your version is below Firefox 157, Firefox ESR 115.42, Firefox ESR 140.17, or Firefox ESR 153.4, the system is vulnerable.

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

The provided CVE data does not specify direct impacts on compliance with standards like GDPR or HIPAA. However, the vulnerability's high CVSS score (8.8) and classification as a use-after-free issue in a critical component suggest potential risks to data confidentiality, integrity, and availability, which could indirectly affect compliance if exploited.

Mitigation Strategies

Update Firefox ESR to version 153.4 or later, Firefox to version 157 or later, or Firefox ESR to version 115.42 or later, or Firefox ESR to version 140.17 or later.

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