Summary
Server-Side Request Forgery in ftp-srv
Background
The FTP protocol creates two connections, one for commands and one for transferring data.
This second data connection can be created in two ways, on the server by sending the PASV command, or on the client by sending the PORT command.
The PORT command sends the IP and port for the server to connect to the client with.
Issue
Since the client can send an arbitrary IP with the PORT command, this can be used to cause the server to make a connection elsewhere.
Workarounds
Blacklisting the FTP Command PORT will prevent the server from exposing this behaviour through active connections until a fix is applied.
const ftp = new FtpSrv({
blacklist: ['PORT']
});
References
https://www.npmjs.com/advisories/1445
Credits
Thank you to;
@trs for fixing it
@andreeleuterio for reporting it to us for an anonymous user (Vincent) through the NPM platform
@quiquelhappy for bringing it to our attention after it slipped through the cracks during Christmas
For more information
If you have any questions or comments about this advisory:
- Open an issue at https://github.com/autovance/ftp-srv
- Email us directly; [email protected]
Impact
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
CVE-2020-15152 has a CVSS score of 9.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.19.6, 3.1.2, 4.3.4); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
- fix: disallow PORT connections to alternate hosts: e449e75219d918c400dec65b4b0759f60476abca
Deprecation notices have been published for older versions.
Frequently Asked Questions
- What is CVE-2020-15152? CVE-2020-15152 is a critical-severity server-side request forgery (SSRF) vulnerability in ftp-srv (npm), affecting versions >= 1.0.0, < 2.19.6. It is fixed in 2.19.6, 3.1.2, 4.3.4. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
- How severe is CVE-2020-15152? CVE-2020-15152 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of ftp-srv are affected by CVE-2020-15152? ftp-srv (npm) versions >= 1.0.0, < 2.19.6 is affected.
- Is there a fix for CVE-2020-15152? Yes. CVE-2020-15152 is fixed in 2.19.6, 3.1.2, 4.3.4. Upgrade to this version or later.
- Is CVE-2020-15152 exploitable, and should I be worried? Whether CVE-2020-15152 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2020-15152 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2020-15152?
- Upgrade
ftp-srvto 2.19.6 or later - Upgrade
ftp-srvto 3.1.2 or later - Upgrade
ftp-srvto 4.3.4 or later
- Upgrade