Is CVE-2026-109781 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-109781 being exploited in the wild.

How severe is CVE-2026-109781?

Medium severity, with a CVSS score of 6.5, published 13 October 2026.

Which products and versions are affected?

Mozilla Firefox before 158; Mozilla Firefox ESR before 153.5; Mozilla Thunderbird before 158; Mozilla Thunderbird ESR before 153.5.

Is there a fix for CVE-2026-109781?

Yes: fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-109781 attacked?

It is attacked over the network, in a web application.

Am I affected by CVE-2026-109781?

Check whether you run Mozilla Firefox, Mozilla Firefox ESR, Mozilla Thunderbird or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-109781: Mozilla Firefox denial-of-service in Printing: Output

CVE-2026-109781 · Severity: medium · CVSS 6.5 · Published 2026-10-13

Firefox and Thunderbird's printing component contains a vulnerability that can cause the application to crash or become unresponsive. An attacker could exploit this by tricking a user into printing a malicious document, resulting in application downtime but not data exposure or system compromise.

Technologies: Mozilla Firefox, Mozilla Firefox ESR, Mozilla Thunderbird, Mozilla Thunderbird ESR. Vendors: Mozilla.

Quick answers

Is CVE-2026-109781 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-109781 being exploited in the wild.
How severe is CVE-2026-109781?: Medium severity, with a CVSS score of 6.5, published 13 October 2026.
Which products and versions are affected?: Mozilla Firefox before 158; Mozilla Firefox ESR before 153.5; Mozilla Thunderbird before 158; Mozilla Thunderbird ESR before 153.5.
Is there a fix for CVE-2026-109781?: Yes: fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-109781 attacked?: It is attacked over the network, in a web application.
Am I affected by CVE-2026-109781?: Check whether you run Mozilla Firefox, Mozilla Firefox ESR, Mozilla Thunderbird or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5

Technical details

A denial-of-service flaw exists in the Printing: Output component, allowing an attacker to crash or hang the browser/email client via a malicious print job. The vulnerability is triggered through user interaction (printing) and has been patched in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Affected products

Mozilla Firefox before 158
Mozilla Firefox ESR before 153.5
Mozilla Thunderbird before 158
Mozilla Thunderbird ESR before 153.5

Timeline

2026-10-13: disclosed

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.