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

Source: https://junglewise.ai/threats/cve-2026-109781-denial-of-service-in-the-printing-output-component-this  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

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](https://junglewise.ai/threats/technologies/firefox), [Mozilla Firefox ESR](https://junglewise.ai/threats/technologies/firefox-esr), [Mozilla Thunderbird](https://junglewise.ai/threats/technologies/thunderbird), [Mozilla Thunderbird ESR](https://junglewise.ai/threats/technologies/thunderbird-esr). Vendors: [Mozilla](https://junglewise.ai/threats/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

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2072852](https://bugzilla.mozilla.org/show_bug.cgi?id=2072852)
- [https://www.mozilla.org/security/advisories/mfsa2026-106/](https://www.mozilla.org/security/advisories/mfsa2026-106/)

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