---
id: "CVE-2026-117973"
kind: "vulnerability"
aliases: ["CVE-2026-117973"]
title: "Firefox: use-after-free in DNS networking lets attackers run code"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["browser", "desktop", "firefox", "runtime"]
not_affected_if: ["already-patched"]
published_at: "2026-10-27T14:16:55+00:00"
first_seen_at: "2026-10-27T14:32:24+00:00"
updated_at: "2026-10-27T14:35:15+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117973", "first_seen_at": "2026-10-27T14:32:24+00:00"}]
---

# Firefox: use-after-free in DNS networking lets attackers run code

A use-after-free flaw in Firefox's DNS networking component lets memory be reused after it is freed. The sources do not say what an attacker can do beyond that, so the reach and the impact are not confirmed.

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

## How to check

- Run `firefox --version` or check Help > About Firefox and compare with `159` or `153.6`
- For ESR installs, check that the version is at least `153.6`

## Fix

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

## Timeline

- 2026-10-27T14:32:24+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117973

## From the sources

Use-after-free in the Networking: DNS 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_