CVE-2026-118176

UNKNOWN 0.0

Bypass of remote UNC path restriction in mailbox: URLs

CVSS Score

0.0

EPSS Score

0.0%

EPSS Percentile

0th

Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name and NTLM authentication data, which could be used for offline password cracking or relay attacks. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

Vendor	mozilla
Product	thunderbird
Ecosystems	Browser JavaScript
Industries	Technology
Published	Oct 27, 2026
Last Updated	Oct 27, 2026

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Affected Versions

Mozilla / Thunderbird

All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗

bugzilla.mozilla.org: https://bugzilla.mozilla.org/show_bug.cgi?id=2081141 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-121/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-122/

Credits

YuYoung Sung