---
id: "CVE-2026-117963"
kind: "vulnerability"
aliases: ["CVE-2026-117963"]
title: "Firefox: service worker boundary bug fixed in versions 159 and ESR 153.6"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["browsers", "desktop", "firefox", "runtime"]
not_affected_if: ["already-on-fixed-version"]
published_at: "2026-10-27T14:16:52+00:00"
first_seen_at: "2026-10-27T14:32:24+00:00"
updated_at: "2026-10-27T14:35:25+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117963", "first_seen_at": "2026-10-27T14:32:24+00:00"}]
---

# Firefox: service worker boundary bug fixed in versions 159 and ESR 153.6

Firefox's Service Workers component has an incorrect boundary condition in the DOM code. The sources do not say what an attacker gets from it.

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

## How to check

- Check the installed Firefox version in Help > About Firefox, or run `firefox --version`
- Check whether the browser is a Firefox ESR build below `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-2026-117963

## From the sources

Incorrect boundary conditions in the DOM: Service Workers component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.

---

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