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electerm has Path Traversal in Zmodem and Trzsz Download Filename Handling

High severity GitHub Reviewed Published May 29, 2026 in electerm/electerm • Updated Jul 2, 2026

Package

npm electerm (npm)

Affected versions

<= 3.11.0

Patched versions

3.11.11

Description

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

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

References

@zxdong262 zxdong262 published to electerm/electerm May 29, 2026
Published to the GitHub Advisory Database Jul 2, 2026
Reviewed Jul 2, 2026
Last updated Jul 2, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(11th percentile)

Weaknesses

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Learn more on MITRE.

CVE ID

CVE-2026-49253

GHSA ID

GHSA-38j7-23hf-9mhc

Source code

Credits

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