---
id: "CVE-2026-117966"
kind: "vulnerability"
aliases: ["CVE-2026-117966"]
title: "Firefox: site isolation flaw in HTTP networking component fixed"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["desktop-browsers", "firefox", "other"]
not_affected_if: []
published_at: "2026-10-27T14:16:54+00:00"
first_seen_at: "2026-10-27T14:32:24+00:00"
updated_at: "2026-10-27T14:35:23+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117966", "first_seen_at": "2026-10-27T14:32:24+00:00"}]
---

# Firefox: site isolation flaw in HTTP networking component fixed

Mozilla fixed a site isolation issue in the Networking HTTP component of Firefox in versions 159, ESR 115.44 and ESR 153.6. The sources do not describe what an attacker can read or do through it.

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

## How to check

- Run `firefox --version` or check Help > About Firefox and compare against `159`, `115.44` (ESR) or `153.6` (ESR)
- unknown for any other check, since the sources do not say

## Fix

- Update Firefox to `159`, or ESR to `115.44` or `153.6`

## Timeline

- 2026-10-27T14:32:24+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117966

## From the sources

Site isolation issue in the Networking: HTTP component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.

---

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