CVE-2026-117921: Use-after-free in the CSS Parsing and Computation component

Published Oct 27, 2026
·
Updated

Use-after-free in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.

Affected Software

3 affected componentsFixes available
Mozilla Firefox ESR<115.44
115.44
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 115.44
  2. Upgrade

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

    Fixed in 153.6
  3. Upgrade

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

    Fixed in 159
  4. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 159
  5. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 115.44
  6. 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 contain the fix?

The issue was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.

2

How can I determine whether a Firefox installation is affected?

Check the installed Firefox version. Installations earlier than Firefox 159 or the listed ESR fixed versions should be evaluated for updating.

Company

Resources

Contact

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