# CVE-2026-109766: Firefox mitigation bypass in Enterprise Policies

Source: https://junglewise.ai/threats/cve-2026-109766-mitigation-bypass-in-the-enterprise-policies-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-2026-109766 · 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](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-2026-109766 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

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2074406](https://bugzilla.mozilla.org/show_bug.cgi?id=2074406)
- [https://www.mozilla.org/security/advisories/mfsa2026-106/](https://www.mozilla.org/security/advisories/mfsa2026-106/)

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