# CVE-2026-44240: basic-ftp denial of service via unbounded multiline response buffering

Source: https://junglewise.ai/threats/cve-2026-44240-basic-ftp-denial-of-service-via-unbounded-multiline-control  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-12. Updated: 2026-05-14  
License: CC BY 4.0 with a link back

CVE-2026-44240 · Severity: high · CVSS 7.5 · Published 2026-05-12

The basic-ftp library, a tool used by Node.js applications to transfer files, is vulnerable to a denial-of-service attack. A malicious or compromised FTP server can send an endless stream of data during the initial connection phase, causing the client application to consume excessive memory and CPU power. This can lead to application crashes, system slowdowns, or service outages for any software that automatically connects to external FTP endpoints.

Technologies: [basic-ftp (npm)](https://junglewise.ai/threats/technologies/basic-ftp). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-44240 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-44240 being exploited in the wild.

**How severe is CVE-2026-44240?** High severity, with a CVSS score of 7.5, published 12 May 2026.

**Which products and versions are affected?** basic-ftp (npm) <= 5.3.0, SEMVER:introduced=0,fixed=5.3.1.

**Is there a fix for CVE-2026-44240?** Yes. basic-ftp (npm): upgrade to 5.3.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-44240 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-44240?** Check whether you run basic-ftp (npm) 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 5.3.1 or later

  ```sh
  npm install basic-ftp@5.3.1
  ```


## Technical details

A vulnerability exists in basic-ftp versions prior to 5.3.1 due to improper resource consumption management in the FTP control channel parser. When a server sends a multiline response (e.g., a banner starting with '220-') that is never terminated, the client appends all incoming data to an internal buffer (`_partialResponse`) and repeatedly reparses the entire accumulated string. Because there is no maximum size limit enforced on this buffer, a malicious server can force the client to consume unbounded memory and CPU cycles. This attack occurs during the initial connection phase before authentication, meaning no credentials are required. The issue is fixed in version 5.3.1 by implementing limits on control response sizes.

## Affected products

- patrickjuchli basic-ftp < 5.3.1

## Identifiers

- CVE-2026-44240
- GHSA-rpmf-866q-6p89

## Timeline

- 2026-04-28: advisory: GitHub Security Advisory published by maintainer
- 2026-05-12: disclosed: CVE-2026-44240 published to NVD
- 2026-05-12: patched: Fix released in version 5.3.1

## References

- [https://github.com/patrickjuchli/basic-ftp/security/advisories/GHSA-rpmf-866q-6p89](https://github.com/patrickjuchli/basic-ftp/security/advisories/GHSA-rpmf-866q-6p89)

## 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 MLSD parser prototype pollution](https://junglewise.ai/threats/cve-2026-126345-basic-ftp-uncaught-typeerror-in-mlsd-directory-listing-parser)
- [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 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)