---
id: "CVE-2026-117898"
kind: "vulnerability"
aliases: ["CVE-2026-117898"]
title: "Firefox: JIT engine use-after-free flaw fixed in version 159"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["browsers", "desktop", "firefox", "runtime"]
not_affected_if: ["esr-153.6-or-later", "firefox-159-or-later"]
published_at: "2026-10-27T14:16:45+00:00"
first_seen_at: "2026-10-27T14:32:22+00:00"
updated_at: "2026-10-27T14:37:41+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117898", "first_seen_at": "2026-10-27T14:32:22+00:00"}]
---

# Firefox: JIT engine use-after-free flaw fixed in version 159

A use-after-free bug in the JIT component of Firefox's JavaScript engine lets memory be reused after it is freed. The sources do not say what an attacker can achieve with it beyond that.

_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 against the fixed versions `159` and ESR `153.6`
- unknown for any other check

## Fix

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

## Timeline

- 2026-10-27T14:32:22+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117898

## From the sources

Use-after-free in the JavaScript Engine: JIT 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_