---
id: "CVE-2026-117976"
kind: "vulnerability"
aliases: ["CVE-2026-117976"]
title: "Firefox: DOM navigation flaw breaks site isolation, fixed in 159"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["desktop-browsers", "firefox", "other"]
not_affected_if: ["firefox-159-or-later", "firefox-esr-153.6-or-later"]
published_at: "2026-10-27T14:16:55+00:00"
first_seen_at: "2026-10-27T14:32:24+00:00"
updated_at: "2026-10-27T14:35:14+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117976", "first_seen_at": "2026-10-27T14:32:24+00:00"}]
---

# Firefox: DOM navigation flaw breaks site isolation, fixed in 159

A site isolation issue in the DOM Navigation component of Firefox was fixed in Firefox 159 and Firefox ESR 153.6. The sources do not say 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, for example by opening Help > About Firefox or running `firefox --version`, and compare it with `159` and `153.6`.

## Fix

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

## Timeline

- 2026-10-27T14:32:24+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117976

## From the sources

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

---

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