CVE-2026-16375: Site isolation issue in the Networking: HTTP component

Published Jul 21, 2026
·
Updated

Site isolation issue in the Networking: HTTP component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

Affected Software

10 affected componentsFixes available
Mozilla Firefox=153
Mozilla Firefox ESR=140.13
Mozilla Firefox<153
153
Mozilla Firefox ESR<140.13
140.13
Mozilla Thunderbird<140.13
140.13
Mozilla Thunderbird<153
153
Mozilla Firefox<140.13.0
Mozilla Firefox<153.0.0
Mozilla Thunderbird<140.13.0
Mozilla Thunderbird>=141.0<153.0

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
  2. Upgrade

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

    Fixed in 140.13
  3. Upgrade

    Upgrade Mozilla Firefox to a version that resolves this vulnerability.

    Fixed in 153
  4. Upgrade

    Upgrade Mozilla Firefox ESR to a version that resolves this vulnerability.

    Fixed in 140.13
  5. Upgrade

    Upgrade Mozilla Thunderbird to a version that resolves this vulnerability.

    Fixed in 153
  6. Upgrade

    Upgrade Mozilla Thunderbird 140.13 to a version that resolves this vulnerability.

    Fixed in 140.13

Event History

Jul 21, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
Updated
via Mozilla·12:00 AM
Affected Software
CVE Published
via MITRE·12:37 PM
Data Sourced
via MITRE·12:37 PM
Description
Data Sourced
via NVD·01:17 PM
DescriptionSeverityWeaknessAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

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Frequently Asked Questions

1

What is the severity of CVE-2026-16375?

CVE-2026-16375 has a critical severity score of 9.8.

2

How do I fix CVE-2026-16375?

You can fix CVE-2026-16375 by updating to Firefox 153, Firefox ESR 140.13, Thunderbird 153, or Thunderbird 140.13.

3

What component is affected by CVE-2026-16375?

CVE-2026-16375 affects the Networking: HTTP component due to a site isolation issue.

4

When was CVE-2026-16375 published?

CVE-2026-16375 was published on July 21, 2026.

5

What products are impacted by CVE-2026-16375?

CVE-2026-16375 impacts Mozilla Firefox, Mozilla Firefox ESR, and Mozilla Thunderbird.

Company

Resources

Contact

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