Is CVE-2026-109707 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-109707 being exploited in the wild.

How severe is CVE-2026-109707?

Critical severity, with a CVSS score of 9.6, 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-2026-109707?

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-2026-109707 attacked?

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

Am I affected by CVE-2026-109707?

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-2026-109707: Firefox sandbox escape in Networking component use-after-free

CVE-2026-109707 · Severity: critical · CVSS 9.6 · Published 2026-10-13

A memory safety vulnerability in Firefox's networking code allows attackers to escape the browser's security sandbox and potentially execute arbitrary code on the user's system. The flaw was fixed in Firefox 158 and ESR 153.5, and should be applied immediately to prevent exploitation of affected systems.

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

Quick answers

Is CVE-2026-109707 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-109707 being exploited in the wild.
How severe is CVE-2026-109707?: Critical severity, with a CVSS score of 9.6, 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-2026-109707?: 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-2026-109707 attacked?: It is attacked over the network, in a web application.
Am I affected by CVE-2026-109707?: 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 use-after-free vulnerability in Firefox's Networking component allows sandbox escape. The flaw permits attackers to gain code execution outside the browser sandbox, potentially enabling full system compromise. The vulnerability is fixed 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

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