---
id: "CVE-2026-117936"
kind: "vulnerability"
aliases: ["CVE-2026-117936"]
title: "Firefox: use-after-free in DOM core and HTML lets attackers run code"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["browsers", "desktop", "firefox", "runtime"]
not_affected_if: ["already-updated"]
published_at: "2026-10-27T14:16:49+00:00"
first_seen_at: "2026-10-27T14:32:23+00:00"
updated_at: "2026-10-27T14:37:02+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117936", "first_seen_at": "2026-10-27T14:32:23+00:00"}]
---

# Firefox: use-after-free in DOM core and HTML lets attackers run code

A use-after-free bug in the Firefox DOM Core and HTML component reuses memory after it has been freed. The sources do not say what an attacker gains beyond that, so the impact is not confirmed.

_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`.
- Compare it against the fixed releases: Firefox `159`, Firefox ESR `115.44`, or Firefox ESR `153.6`.
- Check whether Firefox ESR is in use on managed machines through the fleet's software inventory.

## Fix

- Update Firefox to `159` or later.
- Update Firefox ESR 115 to `115.44` or later.
- Update Firefox ESR 153 to `153.6` or later.

## Timeline

- 2026-10-27T14:32:23+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117936

## From the sources

Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, 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_