Vulnerability in Thunderbird Allows Unauthorized Calendar Access

CVE-2026-118177

What is CVE-2026-118177?

A security flaw in Thunderbird's handling of calendar locations during account setup or network calendar addition allows malicious actors to direct users to unauthorized servers or file shares. This issue becomes particularly critical when using plain HTTP; an attacker could exploit this to induce Thunderbird to subscribe to harmful calendar locations. For users on Windows, this could lead to the exposure of NTLM credentials during calendar refreshes, creating an avenue for unauthorized access and potential overwriting of local files.

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