Calendar discovery accepted local file and remote network share locations

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.

Source published

27 Oct 2026 18:16:31 UTC

Source modified

27 Oct 2026 18:27:49 UTC

Observed here

27 Oct 2026 19:45:55 UTC

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