Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be
Source GCVE Database
Not known to be exploited · fixed in 153.6 : patch Thunderbird soon.
Data as of 27 Oct 2026, 22:14 UTC
Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD
- Patch
- Available – fixed in 153.6
Exploitation evidence
Disclosed: evidence found.
CVE published 27 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
AI-suggested
This vulnerability has been fixed in Thunderbird versions 159 and 153.6. Users should update to one of these versions or later to mitigate the risk. No additional mitigation steps are required if the software is updated.
Description
A vulnerability in Thunderbird on Windows allows bypassing a security check that prevents mailbox: URLs from accessing files on remote Windows network shares by using extended-length UNC paths. This can cause Thunderbird to connect to an attacker-controlled SMB server, leaking the user's Windows account name and NTLM authentication data. The leaked NTLM data could be used for offline password cracking or relay attacks. This issue affects only Thunderbird on Windows and was fixed in Thunderbird versions 159 and 153.6.