Site Isolation Vulnerability in Firefox by Mozilla
CVE-2026-109759

Currently unrated

Key Information:

Vendor: Mozilla
Status: Firefox
Vendor: CVE Published:; 13 October 2026

What is CVE-2026-109759?

A site isolation vulnerability has been identified in the Networking component of Firefox, potentially compromising user security. This issue affects specific versions, namely Firefox 158 and Firefox ESR 153.5, and has been addressed in security updates released by Mozilla. Users are strongly advised to update to the latest versions to safeguard against potential exploits that could arise from this vulnerability.

Affected Version(s)

Firefox 153.5

Firefox 158

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2070252

https://www.mozilla.org/security/advisories/mfsa2026-106/

https://www.mozilla.org/security/advisories/mfsa2026-108/

Download the Critical Vulnerability Management Cheat Sheet

Timeline

Vulnerability published
Oct 13, 2026
Vulnerability Reserved
Oct 13, 2026

Credit

Myungyong Lee

CVE-2026-109759 Data

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