Is CVE-2026-109766 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-109766 being exploited in the wild.

How severe is CVE-2026-109766?

Informational severity, 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-2026-109766?

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

Am I affected by CVE-2026-109766?

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-2026-109766: Firefox mitigation bypass in Enterprise Policies

CVE-2026-109766 · Severity: info · Published 2026-10-13

Firefox and Thunderbird include an Enterprise Policies component that enforces security and compliance requirements set by administrators. A mitigation bypass in this component allows attackers to circumvent these administrator-imposed restrictions, potentially enabling unauthorized system modifications or configuration changes that should be blocked.

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

Quick answers

Is CVE-2026-109766 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-109766 being exploited in the wild.
How severe is CVE-2026-109766?: Informational severity, 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-2026-109766?: Yes: fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird ESR 153.5. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-109766 attacked?: It is in a web application.
Am I affected by CVE-2026-109766?: 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 ESR 153.5

Technical details

CVE-2026-109737 is a mitigation bypass in the Enterprise Policies component affecting Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR. The vulnerability allows an attacker to circumvent policy enforcement mechanisms; the exact attack vector and preconditions are not detailed in available sources. The issue 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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