---
id: "CVE-2026-117864"
kind: "vulnerability"
aliases: ["CVE-2026-117864"]
title: "Firefox: Form Manager sandbox escape fixed in Firefox 159"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["desktop-browsers", "firefox", "other"]
not_affected_if: ["already-updated"]
published_at: "2026-10-27T14:16:40+00:00"
first_seen_at: "2026-10-27T14:32:21+00:00"
updated_at: "2026-10-27T14:39:21+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117864", "first_seen_at": "2026-10-27T14:32:21+00:00"}]
---

# Firefox: Form Manager sandbox escape fixed in Firefox 159

A flaw in the Form Manager component of Firefox allows escape from the browser sandbox. The sources do not say what an attacker gains after escaping.

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

## How to check

- Check the installed Firefox version: `firefox --version`
- Confirm whether Firefox ESR is in use and its version: `firefox --version` on the ESR install

## Fix

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

## Timeline

- 2026-10-27T14:32:21+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117864

## From the sources

Sandbox escape in the Form Manager component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_