CVE-2017-20203
CRITICALDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v4 Vector
Exploitability
Impact
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Exploit Intelligence
Moderate risk: more likely to be exploited than 50% of all known CVEs.
References
Related Vulnerabilities
Other CWE-506 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-3094 | Critical | 10.0 | 86% | - | Fix |
| CVE-2025-30066 | High | 8.6 | 70% | KEV | - |
| CVE-2026-33634 | High | 8.8 | 59% | KEV | Fix |
| CVE-2024-4978 | High | 8.4 | 27% | KEV | - |
| CVE-2025-54313 | High | 7.5 | 4.3% | KEV | Fix |
| CVE-2025-30154 | High | 8.6 | 2.4% | KEV | Fix |
Common questions
How do I fix CVE-2017-20203?
No published fix for CVE-2017-20203 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2017-20203 being actively exploited?
Not that we know of. CVE-2017-20203 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.67% is the estimated probability that it will be exploited in the next 30 days. That is higher than 50% of all scored CVEs.
How severe is CVE-2017-20203?
CVE-2017-20203 has a CVSS v4 base score of 9.3, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
Embed a live status badge for CVE-2017-20203
Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-17.