{"id":"CVE-2026-49253","aliases":["GHSA-38j7-23hf-9mhc"],"url":"https://o3.security/vulnerability/CVE-2026-49253","summary":"electerm: Path Traversal in Zmodem and Trzsz Download Filename Handling","details":"### Impact\n\nA 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.\n\nA 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.\n\n**Attack scenario:**\n1. User connects to a malicious SSH server\n2. Attacker initiates a Zmodem or Trzsz file transfer\n3. Attacker supplies a traversal filename (e.g., `../../.bashrc`, `../escaped.txt`)\n4. User accepts the transfer and selects a download directory\n5. File is written outside the selected directory, potentially overwriting sensitive files\n\n**Affected components:**\n- `src/app/server/zmodem.js` - `prepareReceiveFile()` at line 736\n- `src/app/server/trzsz.js` - `getUniqueFilePath()` at line 559, `openSaveFile()` callback, and `savedFilePaths` mapping\n\n### Patches\n\n- https://github.com/electerm/electerm/commit/fde153d677a170c5816368f6586647f3af4ef284\n\n### Workarounds\n\n\nIf upgrading is not immediately possible, users can mitigate this vulnerability by:\n1. Only connecting to trusted SSH servers\n2. Rejecting or canceling any incoming Zmodem or Trzsz file transfers from untrusted sources\n3. Avoiding the use of Zmodem (`sz`/`rz`) and Trzsz (`trz`/`tsz`) commands on untrusted servers","published":"2026-08-19T14:31:55.683Z","modified":"2026-10-29T02:30:39.365110733Z","cvss":{"score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L"},"epss":{"score":0.00387,"percentile":0.32491,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"electerm","fixedVersion":"3.11.11"}],"fix":{"url":"https://github.com/electerm/electerm/commit/fde153d677a170c5816368f6586647f3af4ef284","label":"electerm/electerm@fde153d"},"references":[{"type":"WEB","url":"https://github.com/electerm/electerm/releases/tag/v3.11.11"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49253.json"},{"type":"ADVISORY","url":"https://github.com/electerm/electerm/security/advisories/GHSA-38j7-23hf-9mhc"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49253"},{"type":"FIX","url":"https://github.com/electerm/electerm/commit/fde153d677a170c5816368f6586647f3af4ef284"},{"type":"PACKAGE","url":"https://github.com/electerm/electerm"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-29T02:30:39.365110733Z"}}