---
id: CVE-2026-118177
title: Calendar discovery accepted local file and remote network share locations
summary: >-
  When looking for calendars in a directory on a server, during account setup or
  when adding a new network calendar, Thunderbird accepted calendar locations
  pointing to other servers, local files or network shares. A malicious server,
  or a…
severity: none
vendor: Mozilla
product: Thunderbird
affected:
  - Thunderbird
published: '2026-10-27'
updated: '2026-10-27'
sourceUpdated: '2026-10-27T18:27:49.964Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-118177'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2080924'
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-121/'
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-122/'
tags:
  - cve.org
ingestedAt: '2026-10-27T18:52:10.021Z'
---

## Overview

When looking for calendars in a directory on a server, during account setup or when adding a new network calendar, Thunderbird accepted calendar locations pointing to other servers, local files or network shares. A malicious server, or a network attacker when the lookup used plain HTTP, could make Thunderbird subscribe to such a location. On Windows this could leak the user's NTLM credentials to an attacker-controlled host on every calendar refresh, and changes to the calendar could be written to the attacker's share or overwrite a local file. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

## Affected

- `Thunderbird`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.