CVE-2026-8956: Integer overflow in the Networking: JAR component

Published May 19, 2026
·
Updated

Integer overflow in the Networking: JAR component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Affected Software

8 affected componentsFixes available
Mozilla Firefox<151
151
Mozilla Firefox ESR<140.11
140.11
Mozilla Thunderbird<151
151
Mozilla Thunderbird<140.11
140.11
Mozilla Firefox<140.11.0
Mozilla Firefox<151.0.0
Mozilla Thunderbird<140.11
Mozilla Thunderbird<151.0.0

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 151
  2. Upgrade

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

    Fixed in 140.11
  3. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 151
  4. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 140.11
  5. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 151
  6. Upgrade

    Upgrade Thunderbird 140.11 to a version that resolves this vulnerability.

    Fixed in 140.11

Event History

May 19, 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·12:29 PM
Data Sourced
via MITRE·12:29 PM
Description
Data Sourced
via Red Hat·02:01 PM
DescriptionSeverityAffected Software
Data Sourced
via NVD·02:16 PM
DescriptionSeverityWeaknessAffected Software
Jun 29, 58424
Event
via FIRST·04:30 PM

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Free Weekly Intel

Don't miss critical vulnerabilities

Join thousands of security professionals who receive our weekly digest of trending CVEs, zero-days, and exploited vulnerabilities.

No spam. Unsubscribe anytime.

Frequently Asked Questions

1

What is the severity of CVE-2026-8956?

CVE-2026-8956 has been classified as a critical severity vulnerability due to the potential for exploitation leading to unauthorized access.

2

How do I fix CVE-2026-8956?

To fix CVE-2026-8956, update your Mozilla Firefox or Thunderbird to version 151 or Firefox ESR to version 140.11.

3

What versions are affected by CVE-2026-8956?

CVE-2026-8956 affects Mozilla Firefox versions prior to 151 and Thunderbird versions prior to 151, as well as Firefox ESR and Thunderbird versions prior to 140.11.

4

Is there a workaround for CVE-2026-8956?

There are no recommended workarounds for CVE-2026-8956; the best course of action is to apply the latest software updates.

5

What type of vulnerability is CVE-2026-8956?

CVE-2026-8956 is classified as an integer overflow vulnerability in the Networking: JAR component.

Company

Resources

Contact

SecAlerts Pty Ltd.
132 Wickham Terrace
Fortitude Valley,
QLD 4006, Australia
info@secalerts.co
By using SecAlerts services, you agree to our services end-user license agreement. This website is safeguarded by reCAPTCHA and governed by the Google Privacy Policy and Terms of Service. All names, logos, and brands of products are owned by their respective owners, and any usage of these names, logos, and brands for identification purposes only does not imply endorsement. If you possess any content that requires removal, please get in touch with us.
© 2026 SecAlerts Pty Ltd.
ABN: 70 645 966 203, ACN: 645 966 203