basic-ftp: Uncaught TypeError in MLSD directory-listing parser via __proto__ fact name causes DoS in Client.list()
CVE-2026-126345
Summary basic-ftp's MLSD directory-listing parser (src/parseListMLSD.ts) looks up fact-handler functions in a plain object literal keyed directly by fact names taken from the FTP server's response, with no validation. A directory-listing line containing the fact name "proto" resolves this lookup to Object.prototype (inherited, non-own, non-function) instead of undefined, so the "not a function" guard is bypassed and the code throws TypeError: factHandler is not a function. This TypeError is not an FTPError, so it is not caught by Client.list()'s retry logic and propagates as a rejected promise out of list() and every API built on top of it (list, downloadToDir, uploadFromDir, clearWorkingDir, removeDir). Any FTP server the client connects to — or any on-path attacker on a plaintext (non-TLS) FTP session — can crash the calling application by returning one crafted line in a directory listing. If the application does not wrap every one of these calls in try/catch, the rejection is unhandled and crashes the Node.js process (default behavior since Node 15). Details File: src/parseListMLSD.ts const factHandlersByName: {[key: string]: FactHandler} = { "size": parseSize, "sizd":…
Assessment
- CVSS
- 5.3 (v3.1)
- Severity
- Medium
- Known exploited
- Not listed in CISA KEV
- Exploit availability
- Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
- Published
- 12 November 2026
- Last updated
- 12 November 2026
- Affected
- basic-ftp
- Weakness
- CWE-1321, CWE-248
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
At the source
References
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