CVE-2026-118176
Bypass of remote UNC path restriction in mailbox: URLs
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.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| Thunderbird Mozilla |
≥ 153.6; ≤ 153.* (unaffected, rpm) ≥ 159; ≤ * (unaffected, rpm) |
CNA: mozilla |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 8.1 high |
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N | ADP: CISA-ADP |
| 3.1 / 8.1 high |
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N | NVD: 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2081141CNA: mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-121/CNA: mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-122/CNA: mozilla
- https://bugzilla.mozilla.org/show_bug.cgi?id=2081141[email protected]
- https://www.mozilla.org/security/advisories/mfsa2026-121/[email protected]
- https://www.mozilla.org/security/advisories/mfsa2026-122/[email protected]
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