# CVE-2026-126345: basic-ftp MLSD parser prototype pollution

Source: https://junglewise.ai/threats/cve-2026-126345-basic-ftp-uncaught-typeerror-in-mlsd-directory-listing-parser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-12. Updated: 2026-11-12  
License: CC BY 4.0 with a link back

CVE-2026-126345 · Severity: medium · CVSS 5.3 · Published 2026-11-12

basic-ftp is a Node.js FTP client library used to download and list files from FTP servers. A malicious or compromised FTP server can inject special property names like __proto__ into directory listings, causing the client to crash with a TypeError when parsing. Applications that do not handle this error will terminate under Node.js 15 and later.

Technologies: [basic-ftp (npm)](https://junglewise.ai/threats/technologies/basic-ftp), [Patrick Juchli Basic-Ftp](https://junglewise.ai/threats/technologies/patrick-juchli-basic-ftp). Vendors: [npm](https://junglewise.ai/threats/vendors/npm), [Patrick Juchli](https://junglewise.ai/threats/vendors/patrick-juchli).

## Quick answers

**Is CVE-2026-126345 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-126345 being exploited in the wild.

**How severe is CVE-2026-126345?** Medium severity, with a CVSS score of 5.3, published 12 November 2026.

**Which products and versions are affected?** Basic-Ftp <UNKNOWN>; basic-ftp (npm) <= 6.2.3, SEMVER:introduced=0,fixed=6.2.4; Patrick Juchli Basic-Ftp prior to 6.2.4.

**Is there a fix for CVE-2026-126345?** Yes. basic-ftp (npm): upgrade to 6.2.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-126345 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-126345?** Check whether you run Basic-Ftp, basic-ftp (npm) or Patrick Juchli Basic-Ftp at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- basic-ftp (npm): upgrade to 6.2.4 or later

  ```sh
  npm install basic-ftp@6.2.4
  ```


## Technical details

The MLSD directory listing parser in parseListMLSD.ts unsafely uses untrusted fact names from the FTP server as keys to look up handlers in a plain object dictionary without validating ownership, allowing prototype pollution via __proto__ or constructor properties. When such a property resolves, the code attempts to call Object.prototype as a function, throwing a TypeError that is not wrapped as an FTPError and propagates to callers. This requires either a compromised FTP server or an on-path attacker on plaintext FTP connections.

## Affected products

- Patrick Juchli basic-ftp prior to 6.2.4

## Identifiers

- CVE-2026-126345
- GHSA-5pm8-86m8-9m6r

## Timeline

- 2026-11-12: disclosed
- 2026-10-30: patched: Release v6.2.4

## References

- [https://github.com/patrickjuchli/basic-ftp/commit/a22664a45d889f7d281e5bdd212c68c0a58d0ae6](https://github.com/patrickjuchli/basic-ftp/commit/a22664a45d889f7d281e5bdd212c68c0a58d0ae6)
- [https://github.com/patrickjuchli/basic-ftp/releases/tag/v6.2.4](https://github.com/patrickjuchli/basic-ftp/releases/tag/v6.2.4)

## Related threats

- [basic-ftp unhandled exception in control socket event handler](https://junglewise.ai/threats/cve-2026-126346-basic-ftp-uncaught-exception-crashes-the-node-js-process-when-a)
- [basic-ftp quadratic-time denial of service in Client.list()](https://junglewise.ai/threats/cve-2026-102990-basic-ftp-is-an-ftp-client-for-node-js-prior-to-6-2-1-client)
- [basic-ftp denial of service via unbounded multiline response buffering](https://junglewise.ai/threats/cve-2026-44240-basic-ftp-denial-of-service-via-unbounded-multiline-control)
- [basic-ftp vulnerable to denial of service via unbounded memory consumption in Client.list()](https://junglewise.ai/threats/cve-2026-41324-basic-ftp-vulnerable-to-denial-of-service-via-unbounded-memory)
- [basic-ftp CRLF injection via incomplete validation](https://junglewise.ai/threats/basic-ftp-crlf-injection-via-incomplete-validation-c2967386)