CVE-2026-100822

Analyzed Analyzed - Analysis Complete

HTTP Spoofing in Firefox and Firefox ESR

Publication date: 2026-09-29

Last updated on: 2026-10-13

Assigner: Mozilla Corporation

Description

Spoofing issue in the Networking: HTTP component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-29

Last Modified

2026-10-13

Generated

2026-10-19

AI Q&A

2026-09-29

EPSS Evaluated

2026-10-18

NVD

CVE-2026-100822

EUVD

EUVD-2026-88801

Affected Vendors & Products

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

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-451	The user interface (UI) does not properly represent critical information to the user, allowing the information - or its source - to be obscured or spoofed. This is often a component in phishing attacks.

Attack-Flow Graph

Executive Summary

This is a spoofing vulnerability in the Networking: HTTP component of Firefox. It allows an attacker to impersonate a legitimate website or service by manipulating HTTP responses or requests. The issue was addressed in Firefox ESR 153.4 and Firefox 157.

Detection Guidance

Detection requires checking Firefox version against patched releases. For Firefox ESR, verify version is 153.4 or higher. For standard Firefox, ensure version is 157 or higher. Use about:support in Firefox or run 'firefox --version' in terminal to check.

Impact Analysis

This vulnerability could allow attackers to trick users into visiting fake websites that appear legitimate. This may lead to phishing attacks, credential theft, or malware downloads. Users could unknowingly expose sensitive information or grant unauthorized access to systems.

Mitigation Strategies

Update Firefox ESR to version 153.4 or Firefox to version 157 or later to address the spoofing issue in the Networking: HTTP component.

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