electerm: Path Traversal in Zmodem and Trzsz Download Filename Handling

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

electerm is an open-sourced terminal/ssh/sftp/telnet/serialport/RDP/VNC/Spice/ftp client. Prior to 3.11.11, electerm uses remote-supplied filenames directly with path.join() while receiving Zmodem and Trzsz transfers. In src/app/server/zmodem.js, prepareReceiveFile() joins the filename to the user-selected save path, and in src/app/server/trzsz.js, getUniqueFilePath(), the openSaveFile() callback, and the savedFilePaths mapping construct destinations without sanitization. A malicious SSH server or remote shell can provide a filename containing traversal components such as ../escaped.txt or ../../.bashrc. When the victim accepts the transfer and selects a download directory, electerm can write outside that directory and overwrite files accessible to the desktop user, potentially changing sensitive configuration or impairing availability. This issue is fixed in version 3.11.11.

Source published

19 Aug 2026 14:31:55 UTC

Source modified

21 Aug 2026 19:31:45 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

electerm is an open-sourced terminal/ssh/sftp/telnet/serialport/RDP/VNC/Spice/ftp client. Prior to 3.11.11, electerm uses remote-supplied filenames directly with path.join() while receiving Zmodem and Trzsz transfers. In src/app/server/zmodem.js, prepareReceiveFile() joins the filename to the user-selected save path, and in src/app/server/trzsz.js, getUniqueFilePath(), the openSaveFile() callback, and the savedFilePaths mapping construct destinations without sanitization. A malicious SSH server or remote shell can provide a filename containing traversal components such as ../escaped.txt or ../../.bashrc. When the victim accepts the transfer and selects a download directory, electerm can write outside that directory and overwrite files accessible to the desktop user, potentially changing sensitive configuration or impairing availability. This issue is fixed in version 3.11.11.

Source published

Aug 19, 2026, 2:31:55 PM (timezone not stated)

Source modified

Aug 21, 2026, 7:31:45 PM (timezone not stated)

Observed here

30 Oct 2026 08:52:23 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 7.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

electerm is an open-sourced terminal/ssh/sftp/telnet/serialport/RDP/VNC/Spice/ftp client. Prior to 3.11.11, electerm uses remote-supplied filenames directly with path.join() while receiving Zmodem and Trzsz transfers. In src/app/server/zmodem.js, prepareReceiveFile() joins the filename to the user-selected save path, and in src/app/server/trzsz.js, getUniqueFilePath(), the openSaveFile() callback, and the savedFilePaths mapping construct destinations without sanitization. A malicious SSH server or remote shell can provide a filename containing traversal components such as ../escaped.txt or ../../.bashrc. When the victim accepts the transfer and selects a download directory, electerm can write outside that directory and overwrite files accessible to the desktop user, potentially changing sensitive configuration or impairing availability. This issue is fixed in version 3.11.11.

Source published

19 Aug 2026 15:17:06 UTC

Source modified

27 Oct 2026 13:10:00 UTC

Observed here

27 Oct 2026 13:11:53 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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CVSS 3.1 · [email protected] · Secondary · 7.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

### 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

Source published

2 Jul 2026 19:20:20 UTC

Source modified

2 Jul 2026 19:41:33 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

Publisher rating · HIGH