Quantum Secular Labs / Blog / Advisories

CVE-2017-20203: NetSarang Xmanager Enterprise: Hard-coded credentials or backdoor

CVE-2017-20203 is rated critical with a CVSS v4.0 base score of 9.3. Per its scoring, it can be exploited over the network, without authentication.

Vulnerability 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.

Severity breakdown

CVSS v4.0 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/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

  • Attack vector: Network. Exploitable remotely over the network.
  • Attack complexity: Low. No special conditions; the attack can be repeated reliably.
  • Attack requirements: None. No deployment or execution conditions are needed.
  • Privileges required: None. No account or prior access is needed.
  • User interaction: Active. A user must knowingly take specific action.
  • Confidentiality impact (vulnerable system): High. Total loss of confidentiality.
  • Integrity impact (vulnerable system): High. Total loss of integrity.
  • Availability impact (vulnerable system): None. No effect on availability.
  • Confidentiality impact (subsequent systems): High. Total loss of confidentiality on other systems.
  • Integrity impact (subsequent systems): High. Total loss of integrity on other systems.
  • Availability impact (subsequent systems): None. No availability impact beyond the vulnerable system.

Underlying weakness

CWE-506: Embedded Malicious Code

The product contains code that appears to be malicious in nature.

Affected products

    References