---
id: "CVE-2026-118174"
kind: "vulnerability"
aliases: ["CVE-2026-118174"]
title: "Thunderbird: OpenPGP key attachments leak requests and NTLM credentials on display"
severity: "medium"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["desktop-mail", "package", "thunderbird", "windows"]
not_affected_if: ["fixed-version", "webmail-only"]
published_at: "2026-10-27T19:17:29+00:00"
first_seen_at: "2026-10-27T19:33:18+00:00"
updated_at: "2026-10-27T19:35:13+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118174", "first_seen_at": "2026-10-27T19:33:18+00:00"}]
---

# Thunderbird: OpenPGP key attachments leak requests and NTLM credentials on display

Thunderbird automatically fetched an external OpenPGP key attachment when a message was displayed, even with remote content blocking on. A sender can point that attachment at any URL, so opening the mail sends a request that can leak the user's NTLM credentials on Windows.

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

## How to check

- Run Help > About Thunderbird and compare the version with `153.6.0` or `159.0`
- Check whether the installed version is below `153.6` on the 153 branch or below `159` on newer branches

## Fix

- Update Thunderbird to `159` or `153.6` or later, the versions named in the advisory

## Timeline

- 2026-10-27T19:33:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118174

## From the sources

When a message containing an OpenPGP key attachment was displayed, Thunderbird automatically loaded the attachment's content to offer importing the key. A sender could mark the attachment as an external attachment pointing to an arbitrary URL, which Thunderbird then loaded without any user interaction, bypassing remote content blocking. On Windows, a URL pointing to an attacker-controlled network share could leak the user's NTLM credentials.
The NTLM credential leak only affects Thunderbird on Windows. On other operating systems, the issue allowed a remote request that bypassed remote content blocking. This vulnerability was fixed in Thunderbird 159 and Thunderbird 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_