PowerCMS XMLRPC API vulnerable to OS command injection


PowerCMS XMLRPC API provided by Alfasado Inc. contains an OS command injection vulnerability (CWE-78).

Alfasado Inc. reported this vulnerability to JPCERT/CC to notify users of its solution through JVN. JPCERT/CC and Alfasado Inc. coordinated under the Information Security Early Warning Partnership.
CVSS Severity (What is CVSS?)

CVSS V3 Severity:
Base Metrics 9.8 (Critical) [IPA Score]
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
  • Confidentiality Impact: High
  • Integrity Impact: High
  • Availability Impact: High
CVSS V2 Severity:
Base Metrics 7.5 (High) [IPA Score]
  • Access Vector: Network
  • Access Complexity: Low
  • Authentication: None
  • Confidentiality Impact: Partial
  • Integrity Impact: Partial
  • Availability Impact: Partial
Affected Products

Alfasado Inc.
  • PowerCMS 5.19 and earlier (PowerCMS 5 Series)
  • PowerCMS 4.49 and earlier (PowerCMS 4 Series)
  • PowerCMS 3.295 and earlier (PowerCMS 3 Series)

The developer states that PowerCMS 2 Series and earlier, which are unsupported (End-of-Life, EOL) versions, are affected too.

An arbitrary OS command may be executed by a remote attacker.

In the case that not using XMLRPC API:
  • If using as CGI/FCGI
    • Delete mt-xmlrpc.cgi or remove execute permission to mt-xmlrpc.cgi
  • If using in PSGI
    • By setting environment variable RestrictedPSGIApp xmlrpc, prohibit XMLRPC application

In the case that using XMLRPC API:
[Upgrade the software and Apply the patch]
Update the software to the latest version, and then apply the patch according to the information provided by the developer.

[Apply the workaround]
If an update cannot be applied, applying the following workaround may mitigate the impact of this vulnerability.
  • Restrict access to mt-xmlrpc.cgi (e.g. Restrict access only to trusted connection source, Set HTTP authentication)
Vendor Information

Alfasado Inc.
CWE (What is CWE?)

  1. OS Command Injection(CWE-78) [IPA Evaluation]
CVE (What is CVE?)

  1. CVE-2021-20850

  1. JVN : JVN#17645965
Revision History

  • [2021/11/24]
      Web page was published