---
id: "CVE-2026-113869"
kind: "vulnerability"
aliases: ["CVE-2026-113869"]
title: "Thunderbird: S/MIME decryption prompt race causes use-after-free crash"
severity: "medium"
cvss: 5.4
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["desktop", "package", "s-mime", "thunderbird"]
not_affected_if: ["no-s-mime", "no-smartcard-or-primary-password"]
published_at: "2026-10-20T20:17:19+00:00"
first_seen_at: "2026-10-23T21:57:21+00:00"
updated_at: "2026-10-25T04:16:28+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-113869", "first_seen_at": "2026-10-23T21:57:21+00:00"}]
---

# Thunderbird: S/MIME decryption prompt race causes use-after-free crash

When Thunderbird asks for a security device password (such as a smartcard PIN or Primary Password) while decrypting an S/MIME message, cancelling or finishing the load frees the message decoder while it is still in use. The resulting use-after-free can crash Thunderbird in a way that may be exploitable for code execution.

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

## How to check

- Run `thunderbird --version` (or check Help > About Thunderbird) and compare against the fixed release `158.0.1`.
- Confirm whether S/MIME is used: Account Settings > End-to-End Encryption lists S/MIME certificates.

## Fix

- Update Thunderbird to `158.0.1` or later.

## Timeline

- 2026-10-23T21:57:21+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-113869

## From the sources

When Thunderbird asked for a security device password (for example a smartcard PIN or the Primary Password) while decrypting an S/MIME message, the message load could finish or be cancelled while the prompt was open. This freed the message decoder while it was still in use, causing a use-after-free and a potentially exploitable crash. This vulnerability was fixed in Thunderbird 158.0.1.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_