CVE-2026-44240 basic-ftp allows a malicious FTP server to cause client-side denial of service via unbounded multiline control response buffering
A malicious FTP server can cause client-side denial of service in basic-ftp by sending unbounded multiline responses, leading to resource exhaustion.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44240?
CVE-2026-44240 is a high-severity denial of service vulnerability in patrickjuchli basic-ftp, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
basic-ftp is an FTP client for Node.js. Prior to 5.3.1, basic-ftp is vulnerable to client-side denial of service when parsing FTP control-channel multiline responses. A malicious or compromised FTP server can send an unterminated multiline response during the initial FTP banner phase, before authentication. The client keeps appending attacker-controlled data into FtpContext._partialResponse and repeatedly reparses the accumulated buffer without enforcing a maximum control response size. As a result, an application using basic-ftp can remain stuck in connect() while memory and CPU usage grow under attacker-controlled input. This can lead to process-level denial of service, container OOM kills, worker restarts, queue backlog, or service degradation in applications that automatically connect to FTP endpoints. This vulnerability is fixed in 5.3.1.
Which versions are affected by CVE-2026-44240?
2 open source packages ship an affected version, including basic-ftp.
| Package | Affected | Fixed in |
|---|---|---|
basic-ftp npm | All versions | 5.3.1 |
basic-ftp npm | All versions | 5.3.1 |
How do I fix CVE-2026-44240?
Upgrade basic-ftp to 5.3.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-44240 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44240 exists.
Sources
Also known as CLEANSTART-2026-DY27694, CLEANSTART-2026-NF21884, CLSA-2026-1780879904, DEBIAN-CVE-2026-44240, ECHO-88de-b7ea-e064, GHSA-rpmf-866q-6p89 and 26 more.