REDHAT-BUG-2517866: Medium severity Mozilla Firefox vulnerability

Q: Which Firefox releases contain the fix?

The issue was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.

Q: Which products should be checked for exposure?

Check Mozilla Firefox and Mozilla Firefox ESR deployments. Versions earlier than the listed fixed releases should be evaluated for update eligibility.

Published Aug 18, 2026

Updated

Same-origin policy bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.

Affected Software

2 affected components

Mozilla Firefox<154

Mozilla Firefox ESR<140.14, <153.1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade Firefox to a version that resolves this vulnerability.
Fixed in 154
Upgrade
Upgrade Firefox ESR to a version that resolves this vulnerability.
Fixed in 140.14
Upgrade
Upgrade Firefox ESR to a version that resolves this vulnerability.
Fixed in 153.1

Event History

Aug 18, 2026

Data Sourced

via Red Hat·12:56 PM

DescriptionSeverityAffected Software

Frequently Asked Questions

Which Firefox releases contain the fix?

The issue was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.

Which products should be checked for exposure?

Check Mozilla Firefox and Mozilla Firefox ESR deployments. Versions earlier than the listed fixed releases should be evaluated for update eligibility.

REDHAT-BUG-2517866: Medium severity Mozilla Firefox vulnerability

Affected Software

Remediation

Event History

Frequently Asked Questions

Which Firefox releases contain the fix?

Which products should be checked for exposure?

Company

Resources

Contact

Frequently Asked Questions

Which Firefox releases contain the fix?

Which products should be checked for exposure?