---
id: "CVE-2026-117959"
kind: "vulnerability"
aliases: ["CVE-2026-117959"]
title: "Firefox: Service Workers site isolation flaw fixed in version 159"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["browsers", "desktop", "firefox", "runtime"]
not_affected_if: ["firefox-159-or-later", "firefox-esr-153.6-or-later"]
published_at: "2026-10-27T14:16:51+00:00"
first_seen_at: "2026-10-27T14:32:24+00:00"
updated_at: "2026-10-27T14:35:29+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117959", "first_seen_at": "2026-10-27T14:32:24+00:00"}]
---

# Firefox: Service Workers site isolation flaw fixed in version 159

A site isolation weakness in the Service Workers component of Firefox's DOM was fixed in Firefox 159 and Firefox ESR 153.6. The sources do not describe what an attacker can read or run through it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Firefox version in the browser's About page or with `firefox --version`
- Check Firefox ESR installs against `153.6`

## Fix

- Update Firefox to `159` or later
- Update Firefox ESR to `153.6` or later

## Timeline

- 2026-10-27T14:32:24+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117959

## From the sources

Site isolation issue in the DOM: Service Workers component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.

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