CVE-2026-117928: Same-origin policy bypass in the CSS Parsing and Computation component

Published Oct 27, 2026
·
Updated

Same-origin policy bypass in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.

Affected Software

2 affected componentsFixes available
Mozilla Firefox ESR<153.6
153.6
Mozilla Firefox<159
159

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 153.6
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 159
  3. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 159
  4. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 153.6

Event History

Oct 27, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
CVE Published
via MITRE·02:05 PM
Data Sourced
via MITRE·02:05 PM
Description

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

Which Firefox versions need to be updated?

The issue was fixed in Firefox 159 and Firefox ESR 153.6. Deploy those versions or later within the affected Firefox and Firefox ESR populations.

2

What security boundary does this vulnerability affect?

It affects the browser same-origin policy through the CSS Parsing and Computation component. A successful exploit could bypass same-origin policy protections.

Company

Resources

Contact

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