All vulnerabilities
CVE-2026-118176

Thunderbird: Bypass of remote UNC path restriction in mailbox: URLs

Mozilla Thunderbird
Open in ThreatlineRecord JSON
CVSS
NoneNot scored
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)No scoreNo FIRST EPSS score in this snapshot yet
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
Published27 Oct 2026Updated 27 Oct 2026CVE List

What fixes it

No source in this snapshot names a fixed version. The vendor advisories under References are the place to check.

Description

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.

Text from CVE List

Affected versions 2

  • Thunderbirdunaffected: 153.6 through 153.*CVE List
  • Thunderbirdunaffected: 159CVE List

References 3