Matrix homeserver could redirect the chat session to a local file or network share

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Summary

CVECVE-2026-118180
StatePUBLISHED
Assignermozilla
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-27 19:17:29 UTC
Updated2026-10-27 19:17:29 UTC
DescriptionWhen 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mozilla Thunderbird unaffected 153.6 153.* rpm Not specified
CNA Mozilla Thunderbird unaffected 159 * rpm Not specified

References

ReferenceSourceLinkTags
bugzilla.mozilla.org/show_bug.cgi [email protected] bugzilla.mozilla.org
www.mozilla.org/security/advisories/mfsa2026-122 [email protected] www.mozilla.org
www.mozilla.org/security/advisories/mfsa2026-121 [email protected] www.mozilla.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Magnus Melin (en)

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