CVE-2026-49253

### Impact A path traversal vulnerability exists in the Zmodem and Trzsz file download handlers in electerm. When receiving files via Zmodem or Trzsz protocols, electerm uses the remote-supplied filename directly in `path.join()` with the user-selected download directory without sanitization. A malicious SSH server or remote shell process can send a specially crafted filename such as `../escaped.txt` to escape the user-selected download directory and write files to arbitrary locations on the user's filesystem, subject to process permissions. **Attack scenario:** 1. User connects to a malicious SSH server 2. Attacker initiates a Zmodem or Trzsz file transfer 3. Attacker supplies a traversal filename (e.g., `../../.bashrc`, `../escaped.txt`) 4. User accepts the transfer and selects a download directory 5. File is written outside the selected directory, potentially overwriting sensitive files **Affected components:** - `src/app/server/zmodem.js` - `prepareReceiveFile()` at line 736 - `src/app/server/trzsz.js` - `getUniqueFilePath()` at line 559, `openSaveFile()` callback, and `savedFilePaths` mapping ### Patches - https://github.com/electerm/electerm/commit/fde153d677a170c5816368f6586647f3af4ef284 ### Workarounds If upgrading is not immediately possible, users can mitigate this vulnerability by: 1. Only connecting to trusted SSH servers 2. Rejecting or canceling any incoming Zmodem or Trzsz file transfers from untrusted sources 3. Avoiding the use of Zmodem (`sz`/`rz`) and Trzsz (`trz`/`tsz`) commands on untrusted servers