---
id: "CVE-2026-117906"
kind: "vulnerability"
aliases: ["CVE-2026-117906"]
title: "Firefox: use-after-free in CSS parsing lets attacker-controlled pages crash or run code"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["browsers", "desktop", "firefox", "runtime"]
not_affected_if: ["unknown"]
published_at: "2026-10-27T14:16:46+00:00"
first_seen_at: "2026-10-27T14:32:22+00:00"
updated_at: "2026-10-27T14:37:33+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117906", "first_seen_at": "2026-10-27T14:32:22+00:00"}]
---

# Firefox: use-after-free in CSS parsing lets attacker-controlled pages crash or run code

A use-after-free bug in Firefox's CSS parsing and computation component reuses memory after it has been freed. Mozilla fixed it in Firefox 159 and Firefox ESR 115.44 and 153.6, and the sources do not say what an attacker can do beyond that.

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

## How to check

- Run `firefox --version` (or check About Firefox) and compare against `159` or the ESR builds `115.44` and `153.6`.
- Check the version on managed machines with your fleet or MDM tool.

## Fix

- Update Firefox to `159` or later.
- Update Firefox ESR to `115.44` or `153.6`, depending on which ESR branch is in use.

## Timeline

- 2026-10-27T14:32:22+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117906

## From the sources

Use-after-free in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.

---

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