# CVE-2026-109767: Mozilla Firefox information disclosure in Networking component

Source: https://junglewise.ai/threats/cve-2026-109767-information-disclosure-in-the-networking-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-2026-109767 · Severity: medium · CVSS 4.3 · Published 2026-10-13

Mozilla Firefox, a web browser used by millions of users worldwide, contains an information disclosure vulnerability in its networking component. An attacker could potentially access sensitive data transmitted or processed by the browser. This vulnerability affects Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR, and has been patched in recent versions.

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-2026-109767 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-109767 being exploited in the wild.

**How severe is CVE-2026-109767?** Medium severity, with a CVSS score of 4.3, 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-2026-109767?** 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-2026-109767 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-109767?** 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

CVE-2026-109767 is an information disclosure vulnerability in the Networking component of Mozilla Firefox and Thunderbird. The vulnerability allows an attacker with network access to potentially disclose sensitive information. The issue has been 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=2074963](https://bugzilla.mozilla.org/show_bug.cgi?id=2074963)
- [https://www.mozilla.org/security/advisories/mfsa2026-106/](https://www.mozilla.org/security/advisories/mfsa2026-106/)

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