7.5 High

CVE-2026-118180 Matrix homeserver could redirect the chat session to a local file or network share

Description

When logging in to a Matrix account, Thunderbird used the homeserver address provided in the server's login response without validating it. A malicious or compromised homeserver could provide a file: URL, causing Thunderbird to send all further Matrix requests of that session to local files or, on Windows, to an attacker-controlled network share, which could leak the user's NTLM credentials. The NTLM credential leak only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

CVSS 3.1 detail

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Exploitable remotely over the network, without an account and without any user action; an attacker can seriously compromise confidentiality, integrity or availability.

Attack vector: Network
Attack complexity: Low
Privileges required: None
Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Affected products and versions

Product	Affected versions	Fixed in
Thunderbird 159	earliest → < 159	159
Thunderbird 153.6	earliest → < 153.6	153.6

References

bugzilla.mozilla.org bugzilla.mozilla.org
www.mozilla.org www.mozilla.org
www.mozilla.org www.mozilla.org

Timeline

Published October 27, 2026
Last modified November 4, 2026

The 1713 CVEs of Thunderbird →

CVE-2026-118179 Request forgery via news: links 8.8 High CVE-2026-118177 Calendar discovery accepted local file and remote network share locations 9.1 Critical CVE-2026-118178 RSS feed could redirect its subscription to a local file or network share 5.7 Medium CVE-2026-118176 Bypass of remote UNC path restriction in mailbox: URLs 8.1 High

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