# CVE-2017-20203: NetSarang v5.0 Malicious Backdoor Supply Chain Compromise

> Attackers can execute arbitrary code and exfiltrate data via a malicious backdoor DLL in NetSarang Xmanager and Xshell products.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 9 Oct 2025
- **Updated:** 21 Nov 2025
- **Also known as:** GHSA-grq9-x3r7-f44p

## What is CVE-2017-20203?

CVE-2017-20203 is a critical vulnerability in NetSarang Computer, Inc. Xftp, published on 9 Oct 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

NetSarang Xmanager Enterprise 5.0 Build 1232, Xmanager 5.0 Build 1045, Xshell 5.0 Build 1322, Xftp 5.0 Build 1218, and Xlpd 5.0 Build 1220 contain a malicious nssock2.dll that implements a multi-stage, DNS-based backdoor. The dormant library contacts a C2 DNS server via a specially crafted TXT record for a month‑generated domain. After receiving a decryption key, it then downloads and executes arbitrary code, creates an encrypted virtual file system (VFS) in the registry, and grants the attacker full remote code execution, data exfiltration, and persistence. NetSarang released builds for each product line that remediated the compromise: Xmanager Enterprise Build 1236, Xmanager Build 1049, Xshell Build 1326, Xftp Build 1222, and Xlpd Build 1224. Kaspersky Lab identified an instance of exploitation in the wild in August 2017.

Weakness: CWE-506 (Embedded Malicious Code)

## Which versions are affected by CVE-2017-20203?


## How do I fix CVE-2017-20203?

No fix has been published for CVE-2017-20203 yet. Limit exposure of the affected software until one is available.

## Is CVE-2017-20203 being exploited?

There is no known exploitation of CVE-2017-20203 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-20203 and fix it if it is affected.

What it is: CVE-2017-20203 is a critical vulnerability in NetSarang Computer, Inc. Xftp, published on 9 Oct 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2017-20203 in the wild and no public exploit code.

Affected product: NetSarang Computer, Inc. Xftp. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2017-20203/ (Markdown: https://insights.sbomify.com/CVE-2017-20203/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-20203
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-20203
- OSV: https://osv.dev/vulnerability/CVE-2017-20203

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-20203/
Summaries are generated and may contain mistakes; the official description above is the record.