---
id: "CVE-2026-113401"
kind: "vulnerability"
aliases: ["CVE-2026-113401"]
title: "Firefox and Thunderbird: PDF Viewer flaw lets a file crash the app"
severity: "medium"
cvss: 6.5
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["desktop", "endpoints", "firefox", "other", "thunderbird"]
not_affected_if: ["default-config-no-pdf-viewing"]
published_at: "2026-10-20T13:16:41+00:00"
first_seen_at: "2026-10-23T21:57:20+00:00"
updated_at: "2026-10-25T03:55:38+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-113401", "first_seen_at": "2026-10-23T21:57:20+00:00"}]
---

# Firefox and Thunderbird: PDF Viewer flaw lets a file crash the app

A flaw in the PDF Viewer component of Firefox and Thunderbird allows a denial of service, meaning a crafted PDF can make the application hang or crash. The sources say the issue was fixed in Firefox 158.0.1 and Thunderbird 158.0.1, and do not describe code execution.

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

## How to check

- Check the installed Firefox version via Help > About Firefox, or `firefox --version` on Linux
- Check the installed Thunderbird version via Help > About Thunderbird, or `thunderbird --version` on Linux

## Fix

- Update Firefox to `158.0.1` or later
- Update Thunderbird to `158.0.1` or later

## Timeline

- 2026-10-23T21:57:20+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-113401

## From the sources

Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 158.0.1 and Thunderbird 158.0.1.

---

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