Tabby Terminal EUVD-2026-55844

Exploitation requires: (1) victim is running Tabby on Windows - the traversal behavior depends on Windows interpreting backslashes as directory separators, so Linux and macOS users are not affected; (2) victim connects to an attacker-controlled or compromised SFTP server; (3) victim initiates a folder download via downloadFolderRecursive() or opens a remote file for inline editing via EditSFTPContextMenu.edit(). These are explicit user-triggered actions. The UI:R CVSS metric correctly captures this dependency. Exploitation is further limited to write-only impact (C:N) - the attacker can place or overwrite files but cannot read victim files through this vector. Tabby versions 1.0.235 and later are not affected.

The CVSS 3.1 vector AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H yields 8.1, which accurately reflects the threat model: network-reachable exploitation with no required privileges on the victim host, but requiring user interaction - the victim must connect to a malicious SFTP server and actively trigger a folder download or file edit. The I:H and A:H ratings are appropriate given that arbitrary file write to the victim's filesystem could overwrite executables, shell scripts, or configuration files. No EPSS score or CISA KEV listing is available, so quantified exploitation probability cannot be confirmed. The Windows-platform specificity (required for backslash-as-separator interpretation) and the need for user-initiated SFTP interaction constrain real-world blast radius to targeted scenarios. This is not a passive or mass-exploitation-friendly vulnerability, but it is a credible attack against users who connect to untrusted SFTP servers.

An attacker stands up a malicious SFTP server and entices a Tabby user on Windows to connect - for example, via a phishing link, a compromised jump host, or a rogue server substituted via DNS manipulation. When the victim browses a directory and downloads a folder or opens a remote file for editing, the server returns filenames containing backslash-encoded traversal sequences such as ..\..\AppData\Roaming\startup-script.bat. Tabby's Electron layer resolves the path via Windows-native path.join(), writing attacker-controlled file content to the traversal destination outside the intended download directory. No public proof-of-concept exploit has been identified at time of analysis.