CVE-2026-118176 Bypass of remote UNC path restriction in mailbox: URLs
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-118176?
CVE-2026-118176 is a vulnerability in Mozilla Thunderbird, published on 27 Oct 2026.
Official 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.
Which versions are affected by CVE-2026-118176?
How do I fix CVE-2026-118176?
No fix has been published for CVE-2026-118176 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-118176 being exploited?
There is no known exploitation of CVE-2026-118176 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-118176, GHSA-g4vf-4v95-x4pc, UBUNTU-CVE-2026-118176.