CVE-2026-100820

Analyzed Analyzed - Analysis Complete

Privilege Escalation in Firefox Address Bar

Publication date: 2026-09-29

Last updated on: 2026-10-05

Assigner: Mozilla Corporation

Description

Privilege escalation in the Address Bar 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:
Percentile:

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-2026-100820

EUVD

EUVD-2026-88799

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	firefox	From 141.0 (inc) to 153.4.0 (exc)
mozilla	thunderbird	to 140.17.0 (exc)
mozilla	thunderbird	From 141.0 (inc) to 153.4.0 (exc)
mozilla	firefox	to 140.17.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-269	The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.

Attack-Flow Graph

Executive Summary

This is a privilege escalation vulnerability in Firefox's Address Bar component. It allows an attacker to gain higher privileges than intended, potentially executing unauthorized actions.

Detection Guidance

This vulnerability affects the Address Bar component in Firefox browsers. To detect it, check the installed Firefox version against the fixed versions: Firefox ESR 153.4, Firefox 157, or Firefox ESR 140.17. Use commands like 'firefox --version' or check 'about:support' in Firefox to verify the version.

Impact Analysis

If exploited, this vulnerability could let attackers take control of your browser session, steal sensitive data, or install malicious software without your knowledge.

Compliance Impact

The vulnerability allows privilege escalation through the Address Bar component, which could lead to unauthorized access or data manipulation. This may impact compliance with GDPR by risking unauthorized data access or processing, and with HIPAA by potentially exposing protected health information. The high CVSS score (8.8) indicates significant risk to confidentiality, integrity, and availability of data.

Mitigation Strategies

Update Firefox ESR to version 153.4 or later, Firefox to version 157 or later, or Firefox ESR to version 140.17 or later to address the privilege escalation in the Address Bar component.

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